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UNAIDS
WHO

ACKNOWLEDGEMENTS

This paper was prepared by James Mclntyre, Perinatal HIV Research Unit, Department of Obstetrics and Gynaecology, University of the Witwatersrand, Johannesburg, South Africa. Additional editing and input was provided by Peter Brocklehurst, Oxford National Perinatal Epidemiology Unit. A working group on HIV in pregnancy, composed of staff from the World Health Organization's Department of Reproductive Health and Research, and the Joint United Nations Programme on HIV/AIDS, oversaw this work and the subsequent review of the paper.

Cover design: Me Nhear

© World Health Organization, 1999
© Joint United Nations Programme on HIV/AIDS, 1999

This document is not a formal publication of the World Health Organization (WHO) and the Joint United Nations Programme on HIV/AIDS (UNAIDS), but all rights are reserved by these agencies. The document may, however, be freely reviewed, abstracted, reproduced and translated, in part or in whole, but not for sale nor for use in conjunction with commercial purposes.

The views expressed in documents by named authors are solely the responsibility of those authors.

For authorization to translate the work in full, and for any use by commercial entities, application and enquiries should be addressed to Department of Reproductive Health and Research, World Health Organization, Geneva, Switzerland, which will be glad to provide the latest information on any changes made to the text, plans for new editions, and the reprint and translations that are already available.

The designations employed and the presentation of the material in this work do not imply the expression of any opinion whatsoever on the part of WHO and UNAIDS concerning the legal status of any country, territory, city or area of its authorities, or concerning the delimitation of its frontiers and boundaries.

The mention of specific companies or of certain manufacturers' products does not imply that they are endorsed or recommended by the World Health Organization in preference to others of a similar nature that are not mentioned. Errors and omissions excepted, the names of proprietary products are distinguished by initial capital letters.

GLOSSARY OF ACRONYMS

3TC	Lamivudine
ADCC	Antibody-dependent cellular cytotoxicity
AIDS	Acquired Immune Deficiency Syndrome
ARV	Antiretroviral
AZT	Azidothymidine (zidovudine)
CD4+	Cluster designation 4 positive lymphocytes
CD8	Cluster designation 8 positive lymphocytes
DNA	Deoxyribonucleic acid
ECS	European Collaborative Study
ELISA	Enzyme-linked immunoabsorbent assay
FDA	Food and Drug Administration, United States of America
HBV	Hepatitis B virus
HIV	Human Immunodeficiency Virus
HIV-1	Human Immunodeficiency Virus Type 1
HIV-2	Human Immunodeficiency Virus Type 2
HIVIG	Hyper-immune HIV immunoglobulin
HLA	Human leukocyte antigen
IgA	Immunoglobulin A
IgM	Immunoglobulin M
IVIG	Intravenous immunoglobulin
MTCT	Mother-to-child transmission
NNRTI	Non-nucleoside reverse transcriptase inhibitor
NSI	Non-syncytium-inducing
PACTG	Pediatric AIDS Clinical Trials Group
PCP	Pneumocystis carinii pneumonia
PCR	Polymerase Chain Reaction
PETRA	Perinatal Transmission Study (UNAIDS)
RNA	Ribonucleic acid
SI	Syncytium-inducing
SLPI	Secretory leukocyte protease inhibitor
STI	Sexually transmitted infection
UNAIDS	Joint United Nations Programme on HIV/AIDS
UNICEF	United Nations Children's Fund
USA	United States of America
WHO	World Health Organization
WITS	Women and Infants Transmission Study
ZDV	Zidovudine

EXECUTIVE SUMMARY

Most of the thirty-three million people living with HIV (human immunodeficiency virus) are in the developing world, where HIV infection in pregnancy has become the most common complication of pregnancy in some countries. More than 70% of all HIV infections are a result of heterosexual transmission and over 90% of infections in children result from mother-to-child transmission (MTCT). Almost 600 000 children are infected by mother-to-child transmission of HIV annually, over 1600 each day. In parts of southern Africa, the prevalence of HIV in pregnant women is over 30%, while rates of new infections are rising in south-east Asia and the proportion of infections occurring in women is increasing in many developed countries. Women are particularly susceptible to HIV infection for both biological and socio-cultural reasons.

Pregnancy does not have a major adverse effect on the natural history of HIV infection in women in most studies, although AIDS (acquired immune deficiency syndrome) has become a leading cause of maternal mortality in some areas, as the epidemic progresses. Adverse pregnancy outcomes that have been reported in HIV positive women include increased rates of spontaneous early abortion, low birth weight babies, stillbirths, preterm labour, preterm rupture of membranes, other sexually transmitted infections, bacterial pneumonia, urinary tract infections and other infectious complications, although whether these are attributable to HIV infection is unknown.

Reported rates of transmission of HIV from mother to child range from 15% to over 40% in the absence of antiretroviral treatment and vary across countries. Transmission can occur in-utero, during labour and delivery or postpartum through breast milk. Most of the transmission is thought to occur in late pregnancy and during labour. Factors associated with an increase in the risk of transmission include viral factors, such as viral load, genotype and phenotype, strain diversity and viral resistance; maternal factors, including clinical and immunological status, nutritional status and behavioural factors such as drug use and sexual practice; obstetric factors such as duration of ruptured membranes, mode of delivery and intrapartum haemorrhage; and infant factors, predominantly related to the increased risk of transmission through breastfeeding.

The use of antiretroviral treatment in pregnancy in a long regimen (as used in the PACTG076 trial) reduces the risk of transmission by two-thirds. Where this has become standard treatment, transmission rates have dropped significantly. Short regimen of zidovudine which is started late in pregnancy and continues until delivery or into the postpartum period appears to decrease transmission risk by 40 to 50%. This relative decrease in risk has been seen in trial populations in which no breastfeeding took place as well as in populations where breastfeeding was practised by the majority of mothers. This observed effectiveness of zidovudine in breastfed infants has not yet been followed-up beyond six months of age. Several studies are in progress on alternative regimens and combination of antiretroviral therapy, which may prove more effective.

Elective Caesarean section also provides protection against mother-to-child transmission, although this is unlikely to be readily available in most developing country settings where HIV prevalence is high. Low serum vitamin A levels have been associated with increased rates of transmission and intervention studies are in progress to evaluate the protective effect of vitamin A and other microbutrients during pregnancy. Vaginal cleansing with Chlorhexidine may be associated with a decreased risk of transmission, and more research is warranted in this field.

Breastfeeding contributes significantly to HIV transmission to children in developing countries. Adequate alternatives to breastfeeding should be provided for HIV-positive women wherever possible. Other possible modifications of infant feeding practices include early cessation of breastfeeding.

HIV testing in pregnancy has a number of benefits, but this must be balanced against the possible risks of stigmatization, discrimination and violence. Voluntary counselling and testing should be encouraged for couples. Post-test counselling is essential following a diagnosis of HIV and should include information about pregnancy-related issues and the risk of mother-to-child transmission. Counselling is also important for HIV-negative women as it provides an opportunity for risk-reduction information to be discussed.

The management of pregnancy in HIV-positive women should be seen as part of the holistic and long-term care of the woman. The medical care of HIV positive women should be tailored to the individual needs of the woman. Obstetric management will be similar to that for uninfected women in most instances, although invasive diagnostic procedures should be avoided, and iron, folate and other vitamin supplementation should be considered. The use of antiretroviral drugs in pregnancy for the prevention of mother-to-child transmission of HIV should be encouraged and provided as widely as possible. In settings where this cannot be implemented in the short-term, other interventions including modifications of obstetric practice should be considered. Postpartum care must include contraceptive advice and provision, infant feeding support and appropriate follow-up for the neonate and the mother.

Universal precautions against occupational exposure to HIV and other pathogens should be in place in maternity services. Basic precautions in obstetric practice include the use of impermeable gloves, the use of a needle holder for suturing episiotomies or vaginal tears and appropriate disposal of needles and blood or liquor contaminated dressings and linen. Where accidental exposure to HIV occurs, by needlestick or other injury, the use of antiretroviral drugs as post-exposure prophylaxis greatly reduces the risk of infection.

INTRODUCTION

At the end of 1998, more than thirty-three million people were living with HIV, almost half of whom were women in their reproductive years^1,2. Over one million children are living with HIV, contracted predominantly through infection from their mothers. The majority of these women and children are in the developing world with two thirds of the infected adults and over 90% of the world's HIV-infected children in Africa. The face of the epidemic is changing as the increasing rate of infection in south-east Asia now accounts for an increasing proportion of new cases. In sub-Saharan Africa, HIV-1-related diseases may account for over 75% of annual deaths in the 15 to 60 age group within the next 15 to 20 years. Life expectancy at age 15 in countries severely affected by the AIDS epidemic could drop from 50 to below 30 years³. It is projected that by 2010, if the spread of HIV has not been contained, AIDS will increase infant mortality by 25 percent and under-five mortality by over 100 percent in the regions most affected by the disease. There have been 8.2 million children who have lost their mothers or both parents to AIDS to date in the epidemic¹, at least 95% of whom have been African.

HIV infection in pregnancy has become the most common complication of pregnancy in some developing countries. This has major implications for the management of pregnancy and birth. With an estimated one and a half million HIV-positive women becoming pregnant each year, almost 600 000 children will be infected by mother-to-child transmission annually: over 1600 each day^1,4. Maternity services in areas of high HIV prevalence have several responsibilities. Firstly, to enable women to be tested and to use these results to maintain their health in an optimal manner; secondly to utilize appropriate interventions to reduce the rate of mother-to-child transmission of HIV; and thirdly to train staff and provide equipment to prevent nosocomial transmission of HIV and other pathogens⁵.

There are two main types of HIV: type 1 (HIV-1) is the most common, with HIV type-2 (HIV-2) found predominantly in West Africa, with some pockets in Angola and Mozambique⁶,⁷. While HIV-1 prevalence is increasing in these areas, the prevalence of HIV-2 has remained fairly stable, and the clinical course of HIV-2 infection is slower than that of HIV-1. Dual infection with HIV-1 and HIV-2 is possible, although it has been suggested that HIV-2 infection may confer some protection against HIV-1 acquisition⁷. Although mother-to-child transmission of HIV-2 has been documented, this occurs less frequently than with HIV-1^8,9. In view of the lesser prevalence of HIV-2 in pregnancy, this document will focus on HIV-1 infection.

The first section of the review consists of a summary of what is known about HIV in pregnancy, transmission of HIV from mother to child, and interventions to prevent transmission. The second part of the review provides some suggestions on the appropriate management of HIV-positive women during pregnancy, delivery and postpartum, and the third section lists guidelines for infection control and safe working conditions with regard to HIV in pregnancy.

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HIV IN PREGNANCY

Epidemiology of HIV

HIV is transmitted in only three ways: through unprotected sexual intercourse, heterosexual or homosexual; through blood or blood products, donated semen or organs; or from an infected mother to her child (vertical or mother-to-child transmission). More than 70% of infections are a result of heterosexual transmission and over 90% of infections in children result from mother-to-child transmission^4,10,11.

Although the HIV epidemic is centred in the developing world, AIDS has also become a leading cause of death for young women in the United States of America (USA)^12,13,14. In developed countries, HIV seropositive women are more likely to be intravenous drug users, partners of drug users or bisexual men, or be involved in sex work ^15,16,17. In one American study, 47% of mothers of HIV-infected infants were intravenous drug users, and 22% reported sex with an intravenous drug user¹⁸.

The situation is very different in developing countries, where heterosexual transmission is the predominant mode of spread. Southern Africa is the most affected region¹. In Kenya, Malawi, Namibia, Rwanda, South Africa, the United Republic of Tanzania, Zambia and Zimbabwe, over 10% of women attending antenatal clinics in urban areas are HIV-positive, with rates of almost 60% in some sites^{1, 10, 19, 20, 21} . To date, Africa has been the centre of the epidemic but a rapid rise in infection rates has been seen in south-east Asia. In Thailand, prevalence in women in antenatal clinics has climbed from 0% in 1989 to 2.3% in 1995 and continues to rise. Similar increases are reported from some Indian cities, Latin America and the Caribbean¹⁰. While prevalence rates in antenatal women have been taken as a good indication of the rate of infection in communities^{22, 23} sentinel surveillance at antenatal clinics may underestimate the population prevalence, as shown in a study in the Mwanza district of the United Republic of Tanzania, where the prevalence in antenatal attenders was below that of the general population by a factor of 0.75²⁴. A decrease in the fertility of HIV-infected women, both from subfertility and from increased early pregnancy loss, as reported from the Rakai district in Uganda, may exacerbate this underestimation²⁵.

In urban Uganda there has been a reported decrease in the prevalence of HIV infections in pregnant women over the past few years. The 20% drop in prevalence is thought to be due to behaviour change following aggressive AIDS education campaigns²⁶.

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Women in the developing world are at higher risk of HIV infection than their male counterparts for a number of reasons, biological and sociological.

Biological factors

The rate of transmission of HIV from male to female is two to three times higher than that from female to male^27,28. The Langerhans' cells of the cervix may provide a portal of entry for HIV and it has been suggested that some HIV serotypes may have higher affinity for these, and therefore to be more efficient in heterosexual transmission²⁹.

Vulval and vaginal inflammation or ulceration may facilitate entry of the virus. Sexually transmitted infections (STI) are common in many African countries, where HIV prevalence is also high^30,31,32. Inadequately treated or "silent" chlamydial and other sexually transmitted infections may act as co-factors for HIV infection and transmission^{33,34,35,36,37,38}. Syphilis rates as high as 30% have been described in antenatal women^39,40 and 4.2% of women in a population based study in the United Republic of Tanzania reported a history of genital ulceration⁴¹, which has been well established as a co-factor for HIV acquisition^42,43,44. In Zimbabwe, women reporting a history of genital ulceration and pelvic inflammatory disease were six times more likely to be HIV-positive⁴⁵. Improved STI treatment in a randomized controlled trial in the United Republic of Tanzania was shown to reduce the rate of new HIV infections⁴⁶. Other non-sexually transmitted cervical lesions, such as schistosomiasis, may also facilitate HIV infection⁴⁷. Although the evidence is still inconclusive, associations between oral and injectable contraceptive use and increased HIV risk have been reported^48,49.

Socio-cultural factors

Women are essentially at more risk in cultures and communities that remove their control over their own bodies. Women are often blamed incorrectly as the source of HIV infection and carry the dual burden of infection and of caring for infected family members. Gender inequalities, poverty, less access to education and lack of employment opportunities force many women into commercial sex work in order to survive, and this group of women are at very high risk of HIV infection^50,51. Conversely, many more women are monogamous, but are at high risk due to the sexual behaviour of their male partner. Traditional practices and customs such as "dry sex" practices, vaginal douching with non antiseptic compounds, female circumcision and "widow cleansing" may all have an effect on increasing women's risk of HIV infection^{51,52,53,54,55,56,57}. Despite their high risk of infection, cultural practices and pressures often prevent women from taking the necessary precautions to guard against infection. Use of male condoms is low in many developing countries. The desire and the societal pressure to reproduce make it difficult for women to practice protected sex. Young women are at highest risk of infections in developing countries, many of them at the beginning of their reproductive lives. Even after a diagnosis of HIV infection, most women will not change their reproductive choices^58,59. There are no methods available for women to use to prevent HIV transmission, independent of the male partner, with the possible exception of the female condom^60,61. Female barrier methods remain expensive or unavailable in most developing countries, where male resistance to condom use is common, although the recent introduction of social marketing of the female condom in some southern African countries has demonstrated that there is considerable demand.

Effect of pregnancy on the natural history of HIV infection

In pregnancy, immune function is suppressed in both HIV-infected and uninfected women^5,62,63. There is a decrease in immunoglobulin, reduced complement levels in early pregnancy and a more significant decrease in cell-mediated immunity during pregnancy. These normal changes during pregnancy have led to concern that the effect of pregnancy among HIV-infected women could be to accelerate the progression of the infection. Early reports of pregnancy in HIV-infected women seemed to support this^64,65. Prospective follow-up studies have not confirmed these findings to date. One French study followed 57 HIV-infected women who completed a pregnancy and 114 who had never been pregnant, with a mean follow-up of 61 months. There was no difference in the rate of acceleration of disease between the groups⁶⁶. An Edinburgh study showed no effect of pregnancy on marker paths of HIV infection in 145 women followed between 1985 and 1992⁶⁷. A further study from Switzerland followed 32 HIV infected pregnant women who had preconception CD4 cell counts and compared their disease progression with 416 HIV infected women who did not have a pregnancy. Women were matched for age and CD4 cell count at entry. Mean follow-up time was 4.8 years for the pregnant women and 3.6 years for the controls. There was no overall difference in the rate of death between the two groups nor in the rate of progression to any AIDS defining event, except that HIV infected women with pregnancies were significantly more likely to develop bacterial pneumonia than their never-pregnant controls⁶⁸.

Several other studies have shown similar results^{63,69,70,71,72,73}. Pregnancy had little effect on viral load in an American study⁷⁴. Pregnancy appears to have little effect on the progress of infection in asymptomatic HIV-positive women or in those with early infection, although there may be more rapid progression in women with late stage HIV infection^75,76,77.

African women do not appear to experience more rapid progression of HIV infection during their pregnancies, despite the additional factors of repeated pregnancies, other infections and poor nutrition. African research does not support the existence of a short-term synergistic effect on the immune system between pregnancy and HIV infection. In a Kenyan study, the difference in the changes over pregnancy in CD4+ and CD8 cells and their ratio were not statistically significant between HIV-positive and negative women⁷⁸. CD4+ and CD8 percentages were shown to be stable in HIV sero-positive women in late pregnancy and the postpartum period in a Malawi study, demonstrating little effect of pregnancy on immune status⁷⁹.

In some central African countries, AIDS has become a common cause of maternal mortality, as the epidemic has progressed^80,81. This does not appear to be due to pregnancy-induced acceleration of the HIV-related conditions but to more women with advanced disease becoming pregnant, with resultant higher rates of HIV complications.

Effect of HIV infection on pregnancy

HIV infection has been reported to have little effect on pregnancy outcome or complications in the developed world^77,82,83,84. It is often difficult to determine the relative contribution of HIV infection, drug use and inadequate antenatal care to adverse outcomes in these women^85,86. Adverse pregnancy outcomes have, however, been reported more commonly in a number of African studies^{87,88,89,90,91} including complications of both early and late pregnancy. HIV may be the direct cause or a marker of a complex interaction of related medical and social conditions that affect pregnancy. Other studies have demonstrated no association⁸⁴. These complication rates vary across studies and may reflect the extent of the epidemic and the nature of HIV-related diseases in different communities.

Complications of early pregnancy have been associated with HIV infection in several studies^{75,77,79,92,93}. HIV-1 and HIV-2 infection in Africa have both been linked to a higher rate of spontaneous abortion⁸. HIV seropositive women were 1.47 times more likely to have had a previous spontaneous abortion, and this rose to 1.81 in women in Uganda who were seropositive for both HIV and syphilis⁹⁴. An American study showed a three-fold increase in early spontaneous abortion in a prospective follow-up study^92,95. More than half of these aborted fetuses had evidence of HIV infection, particularly with the thymus gland affected.

Higher rates of ectopic pregnancy have been reported in HIV-positive women than in uninfected women, which may be related to the effects of other concurrent sexually transmitted infections. Genital tract infections such as Neisseria gonorrhoea, Chlamydia trachomatis, Candida albicans and Trichomonas vaginalis infection have been reported to be more common in women with HIV^96,97. Syphilis is more common in HIV-positive women in African studies. Concurrent infection with syphilis was shown in 33% of HIV-positive pregnant women in South Africa: three times higher than the rate in HIV seronegative women⁹⁶. These high rates of syphilis may confound studies of pregnancy outcome unless the potential bias is taken into account in analysis. All HIV-positive pregnant women should be screened for syphilis, even in low prevalence areas⁹⁷.

Bacterial pneumonia, urinary tract infections and other infections are more common during pregnancy in HIV seropositive women^91,98,99. In addition to these infections and parasitic infestations, any of the HIV-related opportunistic infections can be found during pregnancy. Tuberculosis is the commonest opportunistic infection associated with HIV in the developing world, and particular attention should be paid to its diagnosis in pregnant HIV-positive women. Herpes zoster is common in young HIV-positive women, although uncommon in this age group in the absence of HIV infection¹⁰⁰. Kaposi's sarcoma has been reported during pregnancy in HIV-positive women¹⁰¹.

Preterm labour may be more common in HIV-positive women, with rates as high as double those rates seen in uninfected women in some reports^79,90,102. Preterm rupture of membranes may also be increased in HIV-positive women and abruptio placentae has been described as more common in HIV-positive women in Kenya and South Africa ^{88, 103}.

There is little difference in the birth weight of babies born to HIV-positive mothers in developed countries^104,105. In Edinburgh, HIV seropositivity was associated with a decrease in birth weight, but this was less than the drop attributable to smoking¹⁰⁶. Low birth weight has been reported in some studies in developing countries^100,107. In a Nairobi study, HIV-positive women showed a threefold increase in the risk of delivering a low birth weight baby¹⁰³. This risk was higher with symptomatic HIV infection. In Zambia, the birth weights of babies born to HIV-positive mothers were significantly lower than those of babies of seronegative women. In a prospective study in Rwanda, birth weight was significantly lower in singleton infants of asymptomatic women, although the difference in mean birth weight between the two groups was only 120 g¹⁰⁷. Other studies in predominantly asymptomatic cohorts have shown no significant difference in birth weights¹⁰⁸.

Increased stillbirth rates have been reported, especially from areas where the epidemic has been present for a long time. The risk appears to be lower in asymptomatic women, although stillbirth rates more than double those in HIV sero-negative mothers have been shown in some African centres. However, some of the reported studies do not control for the presence of syphilis or other factors associated with stillbirth. A large study in Nairobi showed an independent association between HIV infection and both intra-uterine and intra-partum death, after controlling for the presence of other STIs⁹⁰.

Infectious complications are also more common during the postpartum period in HIV-positive women^88,102,109. Caesarean section is particularly associated with higher infectious morbidity in some reports, especially in women with low CD4+ counts, with an increased mortality in one Rwandan study^109,110.

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Reported rates of transmission of HIV from mother to child range from around 15%-25% in Europe and the USA to 25% to 40% in some African and Asian studies^111,112. With the advent of routine antiretroviral [ARV] therapy in many developed countries, much lower transmission rates are now being described^113,114. The estimated annual incidence of perinatal infections declined by 27% in the USA between 1992 and 1995 after the widespread implementation of antiretroviral therapy in pregnancy¹⁸.

Transmission of HIV-1 can occur in-utero, at the time of labour and delivery, or postnatally through breastfeeding. Knowledge about the likely timing of transmission is important for the design of possible interventions. Evidence for in utero transmission (as early as 8 weeks gestation) comes from: the detection of HIV-1 and viral antigens (p24) in fetal specimens and placental tissue, viral isolation from some infected infants at the time of birth which implies that transmission occurred before birth; in addition, the observation that some infants get sick very early in life whilst others have a prognosis similar to adults suggests that the first ones (rapid progressors) have acquired infection in utero^{92,115,116,117}.The evidence for intrapartum transmission came first from observations from a register of twins¹¹⁸, which found that the first born twin had a two-fold higher risk of contracting HIV-1 than the second born twin. It is thought that vaginal delivery of the first twin reduces exposure of the second twin to the virus in cervico-vaginal secretions although the same phenomenon is observed for twins delivered by Caesarean section. In addition, recent reports have indicated that mode of delivery may affect the transmission rate. Caesarean section whether elective or emergency has been shown to decrease transmission in some studies¹¹⁹ and prolonged rupture of membranes [more than four hours] to increase the risk of transmission¹²⁰. Around half of the infected infants will have negative viral studies at the time of birth¹¹⁶ indicating that transmission occurred during labour/delivery at the soonest (it takes some days after infection for viral studies to become positive). The evidence for post-partum transmission came from recovery of HIV in both the cell-free and cellular portions of breast milk. In addition, postnatal transmission through breastfeeding is generally assumed to explain most of the differences in transmission rates between developed countries (no or short breastfeeding) and developing countries (prolonged breastfeeding).

The contribution of each of these routes to overall transmission has not been quantified exactly but it appears that in-utero transmission is less frequent and that a substantial proportion of infection occurs at the time of delivery or late in pregnancy^121,122,123. This conclusion is based on the absence of an HIV-1 dysmorphic syndrome, the lack of manifestations of HIV-1 infection at birth and the finding that HIV-1 is detected in the first week of life in only about 50% of children later proven to be infected^{111,113,122,123,124,125,126}. A working definition for the classification of the timing of transmission has been proposed, based on the time of detection of HIV in the infant. Where virus is detectable within 48 hours of birth, an infant is considered to have been infected in utero, while intrapartum infection is assumed if viral studies are negative during the first week of life, but become positive between 7 and 90 days¹²⁷. A Markov model of the time to p24 antigenaemia based on results from the French Collaborative Study group suggested that 65% of infants were infected around the time of labour and 35% in utero¹²⁸. A probability of 27% for in utero transmission was obtained in the Women and Infants Transmission Study (WITS) in the USA¹²⁹, while in Kinshasa, 23% of infants were thought to be infected in utero, 65% intrapartum or early postpartum and 12% in late postpartum¹³⁰.

Factors affecting mother-to-child transmission of HIV-1

Transmission from mother to child of HIV is affected by a number of factors, not all of which have been fully elucidated. These can be divided into viral, maternal, obstetrical, fetal and infant factors as demonstrated in Table 1.

Table 1:Factors affecting mother-to-child transmission of HIV-1^{137, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141}

VIRAL	Viral load
	Viral genotype and phenotype
	Viral resistance
MATERNAL	Maternal immunological status
	Maternal nutritional status
	Maternal clinical status
	Behavioural factors
	Antiretroviral treatment
OBSTETRICAL	Prolonged rupture of membranes (> 4 hours)
	Mode of delivery
	Intrapartum haemorrhage
	Obstetrical procedures
	Invasive fetal monitoring
FETAL	Prematurity
	Genetic
	Multiple pregnancy
INFANT	Breastfeeding
	Gastrointestinal tract factors
	Immature immune system

Viral factors

Viral load

Transmission is increased in the presence of high levels of maternal viraemia. Clinical observations of increased transmission in these situations, such as in advanced disease and at the time of seroconversion, are supported by the presence of high levels of p24 antigenaemia^142,143. With the development of new techniques for the measurement of the virus, such as quantitative Polymerase Chain Reaction (PCR) DNA and RNA, an association has been shown between the maternal viral load and the risk of transmission from mother to child^{144,145,146,147,148,149,150,151,152,153}. More than half of the women with viral loads of>50 000 RNA copies per ml at the time of delivery have been shown to transmit the virus^145,154. A New York study showed a mean viral load of 16 000 RNA copies/ml in transmitters and 6600 RNA copies/ml in non-transmitters¹⁴⁵. Women in this study with measurable viral loads were almost six times more likely to transmit than those in whom the virus was undetectable, after controlling for the CD4+ count. In a French study, transmission rates increased with increasing viral load: 12% in those with less than 1000 copies/ml compared with 29% in those with more than 10 000 copies/ml¹⁴⁴. Few studies have shown a threshold viral load for transmission and it appears that it can occur at low viral levels, for reasons which are not well understood, but which probably reflect the multiple influences acting on mother-to-child transmission^145,154,155.

The local viral load in cervico-vaginal secretions and in breast milk may also be an important determinant of transmission risk intrapartum and through breastfeeding^156,157,158. HIV-1 levels in these fluids have been shown in most studies to be correlated with CD4+ count and plasma viral load^{156,159,160,161}. The presence of sexually transmitted infections or other causes of inflammation, vitamin A deficiency and local immune response may affect viral shedding¹⁶². In Rwanda, postnatal transmission was associated with the presence of HIV-1 infected cells in breast milk¹⁶¹.

Maternal antiretroviral therapy during pregnancy is thought to reduce transmission partly through the reduction of viral load, although the mechanism may also include post-exposure prophylaxis in the child after birth, as the use of zidovudine has been shown to reduce transmission at all levels of maternal viral load^111,146,163. Combination antiretroviral therapy may be more effective in preventing transmission due to the greater reductions in viral load, but no large-scale study results are available yet on this¹⁶⁴.

Viral genotype and phenotype

A number of HIV-1 sub-types or clade groups have been identified, with differing geographical distributions¹⁶⁵. There is little evidence on the effect of sub-type on infection or transmission, although some studies have shown an increased in-vitro ability of sub-type E to infect epithelial cells from the vagina and cervix^156,166. The subtype may affect the cell tropism of the virus, and in turn the infectivity, in-utero, through genital infection or in breast milk.

Most studies on viral variants in mothers and children have demonstrated that the strains in the infant are a distinct subset of maternal virus, although the major maternal variant has also been shown to be transmitted^{149, 156, 131, 167, 168, 169, 170, 171}. Different viral phenotypes show differing tissue tropism. Macrophage-tropic non-syncytium-inducing (NSI) viral isolates appear to be preferentially transmitted to children even when the dominant maternal strains are syncytium inducing (si)^{149,156,131,172,173,174}. There may be a difference in disease progression for the child related to the viral strain. Rapid/high virus isolates have been associated with transmitting mothers whereas slow/low virus isolates were associated with non-transmitting mothers^175,176.

Increased strain diversity in the mother may theoretically influence the rate of transmission. Repeated exposure to different viral strains through pregnancy, occurring through unprotected intercourse may be the mechanism responsible for the observed increase in transmission in these cases¹⁷⁷. The development of resistance to zidovudine during pregnancy has been shown to be infrequent, but concern has been expressed that the possible development of resistant strains of HIV-1 in women receiving zidovudine monotherapy during pregnancy may result in higher transmission rates in subsequent pregnancies^178,179. Since the risk of resistance emergence increases with the duration of treatment and since resistance to AZT usually emerges after 3-4 months of treatment, the emergence of resistance with short-regimen of zidovudine (1 month) is very low and less likely compared to long regimen of zidovudine.

Maternal factors

Maternal immunological status

Transmission from mother to child is more likely with decreased maternal immune status, reflected by low CD4+ counts, low CD4+ percentages or high CD4+/CD8 ratios^5,180. These in turn may be markers for higher viral loads, as opposed to risk factors in themselves, although an interaction between viral load and immune response may be present. In the European Collaborative Study (ECS), there was an increased risk of mother-to-child transmission where maternal CD4+ counts were below 700/cubic mm¹⁴². Transmission increased almost linearly in this study with decreasing CD4+ counts¹⁸¹. Several other studies have noted similar associations^{181,182,183,184}. In the WITS study, the association between low CD4+ percentages and transmission was only seen in women without persistently positive viral cultures. Where there was at least one negative culture and high CD4+ cell percentages, transmission rates were in the range of 1-4%¹⁸².

There have been conflicting results about the role of neutralizing antibodies in preventing transmission. Some studies have shown that high levels of maternal neutralizing antibody are associated with lower rates of transmission, while in others no association was observed^{185,186,187,188}. Women who transmit in-utero may have lower levels of autologous neutralizing antibody than those who do not transmit, or those women where transmission occurs intrapartum¹³¹. Antibody to the V3 loop of HIV-1 envelope gpl20 has not been shown to be protective, neither do antibody-dependent cellular cytotoxicity (ADCC) antibodies appear to be protective^189,190,191. One report has correlated maternal antibodies to the carboxy region of the gp41 envelope glycoprotein with lack of vertical transmission¹⁹². The involvement of specific T-cell immunity in the pathogenesis of mother-to-child transmission has yet to be determined.

Little is known about the role of mucosal HIV-1 antibodies and viral shedding in the genital tract which may affect intrapartum transmission rates^156,160. Infection through breastfeeding has been associated with a lack of IgM and IgA in breast milk^193,194.

Maternal nutritional factors

Serum vitamin A levels in HIV-1 positive mothers have been correlated with the risk of transmission in a Malawi study. The mean vitamin A level in those mothers who transmitted the virus to their children was significantly lower than in those who did not transmit. Women with vitamin A levels below 1.4 umol/1 had a 4.4-fold increased risk of transmission, which dropped with increasing vitamin A levels¹⁹⁵. One US study showed no relationship between low vitamin A levels and transmission¹⁹⁶, while another cohort study did show a correlation¹⁹⁷. The mechanism of vitamin A effect is uncertain, but the influence of vitamin A on the integrity of the vaginal mucosa or placenta and the immune stimulatory properties of the vitamin have been suggested ^{162, 198}. Alternatively, low vitamin A levels may be a marker for other deficiencies or behavioural factors, which influence transmission. Other micronutrients, including zinc and selenium, have been suggested as having a possible role.

Behavioural factors

Several behavioural factors have been associated with an increased rate of transmission from mother to child. These include cigarette smoking^199,200 and maternal hard drug use^119,201,202.

Unprotected sexual intercourse during pregnancy has been linked to an increased risk of mother-to-child transmission. A transmission rate of 30% was shown in women who had more than 80 episodes of unprotected sex during pregnancy compared with 9.1% in those with no unprotected intercourse²⁰³. A similar association is suggested in two African studies^204,205. This may be due to an increased concentration or strain diversity of HIV-1, or the effect of cervical or vaginal inflammation or abrasions. An increase in chorioamnionitis has previously been reported linked to sexual activity in pregnancy²⁰⁶, and this may be an alternative mechanism. The presence of sexually transmitted infection during pregnancy has been correlated with increased risk of transmission²⁰⁷, and STIs have been shown to increase viral shedding in cervico-vaginal secretions³².

Placental factors

Placental factors have been implicated in transmission of the virus from mother to child^{116, 208,209,210,211}.Placental infection with HIV-1 has been reported and Hofbauer cells and possibly trophoblasts express CD4+ and are thus susceptible to infection²¹². An association between increased transmission and the presence of chorioamnionitis was described early in the epidemic. Other placental infections and non-infectious conditions such as abruptio placentae have also been implicated^162,213,214. Breaks in the placental surface can occur at any stage of pregnancy and may be related to transmission, although the significance of these may, in turn, depend upon the maternal viral load²¹⁵. Smoking and drug use, both associated with increased transmission, may exert this effect through placental disruption¹¹⁶. In areas of high malaria prevalence, infection of the placenta is common in pregnancy. Placental P. falciparum infestation has been associated with poorer survival in infants born to HIV-1 positive mothers in Malawi, which may represent increased transmission rates²'⁶ and with higher rates of transmission from mother to child in Kenya²¹⁷.

Obstetric factors

With the majority of mother-to-child transmission occurring at the time of labour and delivery, obstetric factors are important determinants of transmission. Suggested mechanisms for intrapartum transmission of HIV-1 include direct skin and mucous membrane contact between the infant and maternal cervico-vaginal secretions during labour, ingestion of virus from these secretions, and ascending infection to the amniotic fluid^113,207. HIV-1 in cervico-vaginal secretions may be raised four-fold during pregnancy²¹⁸. The higher rate of infection in first-born twins may be due to longer exposure of the infants to infected secretions²¹⁹.

Several obstetric factors have been implicated, although results are not consistent across studies with regard to the relative importance of different obstetric factors. In the French perinatal cohort study, preterm delivery, intrapartum haemorrhage and obstetric procedures were related to transmission risk²⁰⁷. Other factors such as the use of fetal scalp electrodes, episiotomy, vaginal tears and operative delivery have been implicated in some studies but not in others^{113,120,181,214,220}.

The duration of labour does not appear to be as important as the duration of rupture of membranes^182,221. Prolonged rupture of membranes has been associated with increased risk of transmission in a number of studies and is an important risk factor^119,207,222. In an American study, duration of ruptured membranes of over four hours nearly doubled the risk of infection, regardless of the eventual mode of delivery¹¹⁹.

Delivery by Caesarean section has been shown to be protective in some prospective follow-up studies, but not in all^{181,119,223,224,225}. This has now been confirmed in a randomized controlled trial in Europe²²⁶. A Swiss study showed an additive protective effect of elective Caesarean section for women receiving antiretroviral treatment²²⁷. In France, women who received long-course antiretroviral treatment in pregnancy and had an elective Caesarean section had a transmission rate of less than 1%²²⁸.

Fetal factors

Fetal genetic factors may play a part in transmission. Little is known yet about the role of genetic factors such as the CCR-5 delta32 deletion and human leukocyte antigen (HLA) compatibility of mother and infant in the determination of transmission risk^229,230,231. Concordance between infant and maternal HLA has been associated with increased risk of transmission²³².

Preterm infants have higher reported rates of transmission of HIV-1 in several studies^{111,181,220,233}. Women with low CD4+ counts are more likely to have preterm deliveries, which may influence this finding. The higher rates of infection seen in firstborn twins have been widely reported and have formed part of the evidence for the role of intrapartum transmission^234,235. This effect is more pronounced in vaginally delivered twins, where a two fold increase in infection is seen in first born twins over second born, but is also present in twins delivered by Caesarean section²¹⁹.

Other fetal factors may include co-infection with other pathogens, fetal nutrition and fetal immune status¹³².

Infant factors

Breastfeeding is responsible for a high proportion of mother-to-child transmission in developing countries, where 30% or more of perinatal HIV infections will occur through breast milk. This is less common in the developed world, where most HIV-positive women will not breastfeed. Breast milk contains both cell associated and free virus, the amount of which may be related to the immune suppression of the mother and vitamin A levels^159,236. Other protective factors are also present in breast milk, including mucins, HIV antibodies, lactoferrin, and secretory leukocyte protease inhibitor (SLPI)^{111,161,234,132}.

A meta-analysis of studies of transmission through breastfeeding showed the additional risk of transmission through breastfeeding to be between 7 and 22%, equivalent to a doubling of transmission rates ²³⁷. That is to say that, in breastfeeding populations, between one third and one half of mother-to-child transmission occurs during breastfeeding. A Soweto study has shown transmission rates of 18% in formula fed infants compared with 42% in breastfed²³⁸. Rates are higher when the mother sero-converts during breastfeeding, where the estimated additional risk is around 30%^237,239. The risk of breast milk transmission may also depend upon other factors, such as maternal disease stage, breast abscesses, mastitis, nipple cracks, patterns of breastfeeding (i.e. exclusive or mixed), maternal vitamin A and oral thrush in the child^111,193. A Zimbabwe study showed that 31% of breastfeeding mothers of HIV-1 infected children had active nipple disease²⁴⁰.

Late postnatal transmission, after the age of six months, has been described in a number of studies^{111,220,130,241}. In Abidjan, 12% of infants born to HIV-1 positive mothers were diagnosed as HIV-infected after the age of six months but may have been infected earlier²⁴².

The risks of postnatal transmission may also be related to other factors in the newbom. HIV entry may occur through the gastro-intestinal tract following ingestion of virus in utero or at birth⁸³,¹³². There is decreased acidity, decreased mucus, lower IgA activity and thinned mucosa in the newborn gastro-intestinal tract, which may facilitate transmission"''²³⁴'¹³². The newbom immune system may also be deficient in macrophage and T cell immune response¹³², increasing the susceptibility to infection. At least part of the effect of antiretroviral drugs in pregnancy appears to be due to a post exposure prophylaxis effect after birth¹¹³.

Further information on HIV transmission and breastfeeding can be found in the joint UNAIDS, UNICEF and WHO publication A review of HIV transmission through breastfeeding (WHO/FRH/NUT/CHD/98.3/UNAIDS 98.5)/UNICEF/PD/NUT/(J) 98.1.

Interventions to prevent mother-to-child transmission of HIV

With increasing knowledge about the underlying mechanisms of mother-to-child transmission of HIV-1 has come an increased emphasis on the search for interventions to prevent or reduce the risk of transmission^{111,113,243,244}. The successful use of antiretroviral therapy and replacement feeding in developed countries has lead to suggestions that it may eventually be possible to reduce perinatal transmission rates to less than 2%¹³¹. A number of possible intervention strategies have been proposed or are under investigation. These are shown in Table 2.

Table 2:Possible strategies known or under investigation for the prevention of mother-to-child transmission of HIV

TERMINATION OF PREGNANCY BEHAVIOURAL INTERVENTIONS Reduction in the frequency of unprotected sexual intercourse during pregnancy Reduction in the number of sexual partners during pregnancy Lifestyle changes, including avoidance of drug use and smoking in pregnancy THERAPEUTIC INTERVENTIONS Antiretro viral therapy: zidovudine alone or combination, long- or short-regimen Vitamin A and other micronutrients Immunotherapy Treatment of STI OBSTETRIC INTERVENTIONS Avoidance of invasive tests Birth canal cleansing Caesarean section delivery MODIFICATION OF INFANT FEEDING PRACTICE Avoidance of breastfeeding Early cessation of breastfeeding Heat treatment of expressed breast milk

The prevention of new infections in women of reproductive age remains an important component²⁴⁵. This includes the reduction of women's vulnerability to HIV-1 infection through the improvement of women's status in society, the provision of information about HIV/AIDS and its prevention, the promotion of safer sex including the use of barrier methods, and the adequate treatment of sexually transmitted infections^246,247. Women known to be HIV positive should have access to appropriate contraception and information to help them determine their future fertility. Access to termination of pregnancy for HIV positive women can also reduce the burden of paediatric AIDS cases, but should be viewed as an option for individual women, rather than a public health intervention for the prevention of transmission. Most women living with HIV will decide to continue with pregnancy, even where termination is offered^248,249.

Table 3: Some research projects in progress on the prevention of mother-to-child transmission of HIV (1998)

STRATEGY	RESEARCH PROJECTS
A: ANTIRETROVIRAL THERAPY	Phase III:
	1. PETRA: ZDV & 3TC
	2. ZDV alone in short-reginmen in breastfeeding women
	3. Nevirapine (HIVNET 012 & PACTG 316)
	Phase I/II:
	Drugs under investigation include: ddi, d4T, Nevirapine, Melfinavir, Ritonavir, Indinavir, Saquinavir, PMPA, MKC-442
B: ACTIVE IMMUNIZATION	1. Recombinant Gp120 vaccine to pregnant women (PACTG 235).
	2. Recombinant Gp120 to newborns; phase I/II (PACTG 230)
	3. Canary pox vaccine to newborns (PACTG 327)
C: PASSIVE IMMUNIZATION	1. HIVIG (Uganda)
	2. Phase I Katinger antibody
D: MICRON UTRIENTS	1. Vitamin A (Malawi: 10 OOOIU)
	2. Vitamin A (South Africa: 5000 IU+ B Carotene 30 mg)
	3. 13 Vitamin A 10 000 IU and 12 other vitamins and minerals (Zimbabwe)
	4. Factorial design Vitamin A & B Carotene (United Republic of Tanzania)
	5. Vitamin A (Zvitambo) (Zimbabwe) postpartum and to children
E: VAGINAL CLEANSING	Chlorhexidine (Kenya)
F: INFANT FEEDING	Randomized trial of breast vs formula feeding (Kenya)

The only interventions proven to be effective in reducing mother-to-child transmission of HIV at present are the use of zidovudine (either as long-course through pregnancy, labour and for six weeks to the infant, or as short-regimen), Caesarean section and the avoidance of breastfeeding^250,251,226. Research continues into a number of other alternatives, with a major focus on interventions active at the time of labour and delivery, when much of the transmission is believed to occur. Studies that are completed and in the analysis stage include a vitamin A study in Malawi, a randomized formula feeding study conducted in Nairobi and a self-selection study looking at the effects of breastfeeding on transmission in Soweto. Other studies on the effect of vitamin A administration (South Africa, the United Republic of Tanzania and Zimbabwe), vaginal disinfection (Kenya), and short-regimen antiretrovirals are ongoing. Postpartum interventions besides the use of formula feeding have not been studied. These trials are summarized in Table 3.

(introduction...)

The ideal intervention for the reduction of mother-to-child transmission would be one that is widely applicable in resource poor settings²⁵². Vaginal disinfection and vitamin A administration would not require identification of HIV positive women, but would be applicable to all pregnant women. The minimum requirements for the implementation of other interventions in health services include²⁵³:

· access to and use of appropriate antenatal, intrapartum and postpartum care with adequately trained health workers

· adequate pre and post test counselling services

· ability to afford the cost of reliable HIV testing

· appropriate laboratory facilities to monitor blood parameters during long regimen

· delivery units with access to disinfectants, gloves and clean needles

· acceptance and uptake of the intervention by HIV-infected women

· a regimen that is logistically possible to implement in terms of dosing times and routes, drug storage and distribution

· a regimen which is affordable for the health service.

The widespread implementation of strategies to prevent mother-to-child transmission of HIV presents a number of challenges to the existing antenatal and obstetric services. The need for such strategies is greatest in the most resource constrained settings. The provision of interventions to prevent mother-to-child transmission of HIV should not further overburden existing services. In many areas, antenatal care services are not sufficiently available, accessible or utilized and they may not be of adequate quality to take on these interventions. These services will need to be strengthened in the years ahead in order to deliver mother-to-child transmission prevention strategies effectively.

In addition if interventions are introduced into clinical practice to decrease the risk of mother-to-child transmission their effectiveness outside of the context of a randomized controlled trial should be monitored. Careful follow-up of the mothers and infants of such programmes will be essential to determine the generalisability of clinical trial results to the practical setting.

The management of HIV infection and AIDS is changing rapidly. New drugs become available and are rapidly adopted into clinical practice with little rigorous evaluation of their effectiveness. In pregnancy the situation is little different. Within one month in 1999, four substantial randomized trials of interventions aimed at decreasing the risk of mother-to-child transmission of HIV infection were published. Many more trials are on-going and can be expected to report in the next two years. The following section, therefore, represents the evidence that was available at the end of May 1999. As new randomized trials are published they will be incorporated into an ongoing systematic review and meta-analysis of interventions aimed at decreasing the risk of mother-to-child transmission of HIV infection published in the Cochrane Library²⁵⁴.

Antiretroviral therapy

Long-course zidovudine treatment

The success of the Paediatric AIDS Clinical Trials Group (PACTG) trial PACTG076 of the use of zidovudine (ZDV) in pregnancy in asymptomatic women has been a major advance in the prevention of mother-to-child transmission of HIV-1²⁵⁵. Zidovudine given orally after 14 weeks of pregnancy, intravenously during labour and for six weeks to the neonate in a non-breastfed population has been shown to reduce mother-to-child transmission of HIV-1 significantly. This has become the standard of care during pregnancy in many developed countries, with a concomitant decrease in reported transmission rates^111,113.

In this randomized placebo-controlled trial conducted in France and the USA, in a non-breastfeeding population, treatment with ZDV [100 mg 5 times daily] or placebo was started between 14-34 weeks of pregnancy [median 26 weeks]. Women also received intravenous ZDV or placebo during labour and the infants received oral ZDV [2 mg/kg 4 times daily] or placebo for six weeks. All women had CD4+ counts >200 per cubic mm, were symptom free and had not previously received ZDV. The first interim analysis on 356 mother-infant pairs demonstrated a rate of mother-to-child transmission of 25.5% in the placebo group, and 8.3% in the ZDV group. Treatment with ZDV achieved a 67.5% reduction in transmission risk. The drug was well tolerated in the short-term in the pregnant women and the neonates.

The effect of ZDV in reducing transmission appears to be partly through the reduction of maternal viral load, although transmission occurred at a wide range of viral loads in the PACTG076 study^163,256. An additional level of protection through post exposure prophylaxis in the infant is also hypothesized, as ZDV readily crosses the placenta¹¹¹.

Further evidence for a post-exposure effect comes from a retrospective New York State study of the efficacy of abbreviated zidovudine regimens. Women who received ZDV from the prenatal period had a transmission rate of 6.1%. When treatment was commenced intrapartum, transmission was 10%, when started within 48 hours of birth 9.3% and when started on day 3 or later, transmission was 18.4%²⁵⁷,²⁵⁸.

Reassurance that in-utero exposure to zidovudine does not appear to produce any unexpected long-term effects has been supported by a follow-up study among the uninfected children born to women participating in ACTG076²⁵⁹. This study reported follow-up information from 122 uninfected children in the zidovudine group and 112 uninfected children in the placebo group. Median age of the children at time of last follow-up was 4.2 years with a range of 3.2-5.6 years. No differences could be detected in any parameters of growth, cognitive and developmental function assessed by the Bailey Scales of Infant Development, immunologic function, cardiac function or ophthalmologic function. In addition there were no late deaths and no malignancies detected in this group.

The use of long-course ZDV in pregnancy is recommended as the standard of care in Europe, the USA and in some other countries, including Brazil and Thailand^{260,261,262,263,264}. The introduction of this policy has led to a dramatic reduction in the reported transmission rates in France and the USA^18,265,70. In France, a two-thirds reduction in transmission [from 14% to 5%] has been reported²⁶⁵. Transmission rates in Los Angeles have dropped from 30% to 10%, in North Carolina from 21% to 8.5%^131,266. However, the success of the intervention depends upon the access of HIV positive women to therapy. In areas where utilization of antenatal care is low, and thus access to counselling, testing and drug provision is reduced, the efficacy will be lower. This has been shown in the Bronx, New York, where only 40% of HIV-infected women were identified before birth and less than half of these received ZDV²⁶⁷.

The use of ZDV in this regimen is not directly applicable to most women in the developing world where the majority of mother-to-child transmission occurs. This is because of the high cost of the intervention (in the USA the regimen costs over US$ 1000 per mother-child pair); the logistics of monitoring of blood parameters, drug reactions; intravenous infusions during delivery and treatment to the newborn for six weeks. In addition, the intervention needs to be introduced early on in pregnancy, when most women in resource-poor settings only attend antenatal care late in pregnancy. Lack of access to counselling and testing in these settings limits the use of antiretrovirals in pregnancy. Women in developing countries have higher rates of anaemia, which may be exacerbated by antiretroviral treatment, and may differ in disease status from those in developed countries.

The PACTG076 trial was conducted in a non-breastfeeding population, and the efficacy of the regimen in a breastfeeding population needs to be determined, as any reduction in transmission prior to or during labour may be negated by an increased transmission from breast milk^264,268. The acceptability of these interventions in developing countries will require further study ^{111,252,269,270}.

Some resistant strains of virus have been reported after ZDV treatment to prevent transmission^178,179,271. Although resistance appears to be uncommon, there has been concern about the use of ZDV monotherapy in the management in any subsequent pregnancy^179,271.

The results from the PACTG076 trial and the ZDV in Pregnancy Register show as yet no evidence of teratogenicity or short-term adverse effects in the fetus or newborn. In addition follow-up to age four of uninfected children who were exposed to in-utero zidovudine has also revealed no medium term adverse effects²⁵⁹. However, longer term follow-up is still required and larger groups of children need to be followed to determine whether rare but serious adverse effects may occur^131,272,273. However, recent reports of ZDV toxicity in mice^274,275 have renewed concern about the long-term effects of the drug. A consensus panel convened by the National Institutes for Health in early 1997 advised that the evidence was not sufficient to alter the recommendations for the use of ZDV in pregnancy. Children exposed to ZDV in pregnancy should be monitored for long-term toxicity effects.

It has been suggested that ZDV use in pregnancy would be a cost effective intervention in both developed and developing countries if implementation problems can be overcome^{276,277,278,279}. The use of shorter regimens or other antiretroviral drugs provides a feasible alternative.

Short-regimen of zidovudine therapy

Shorter drug regimens in pregnancy would be more feasible in resource-poor settings. Results from some developed country studies suggest that antenatal oral ZDV alone may be as effective as antenatal, intrapartum and postpartum regimens^280,281. To date three randomized trials of short-regimen have been published from resource-poor settings.

A trial of short-regimen zidovudine treatment in Thailand has shown a significant effect in preventing transmission²⁵¹.

The Bangkok Perinatal AZT Study, was a randomized placebo-controlled trial to evaluate the safety and efficacy of a short-regimen of oral zidovudine [ZDV] administered during late pregnancy and labour to reduce the risk for perinatal HIV transmission. The regimen was 300 mg ZDV orally twice daily from 36 weeks gestation until the onset of labour and 300 mg every three hours from the onset of labour until delivery. All women were advised not to breastfeed and were provided with infant formula, and it is important to bear in mind that these results are directly applicable only to formula-fed infants²⁵¹.

Transmission in the treatment group was 9.4% [95% confidence interval, 5.2%-13.5%] and 18.9% [95% confidence interval, 13.2%-24.2%] in the placebo group, representing a 50% reduction in transmission risk [95% confidence interval, 15.4%-70.6%].

A further trial of short-regimen in over 350 women conducted in Burkina Faso and Cd'Ivoire compared placebo with oral zidovudine, started between 36 and 38 weeks gestation at 300mg twice daily, followed by a single loading dose of 600mg at the onset of labour followed by oral zidovudine 300mg twice a day to the mother continued until seven days after delivery²⁸². In this trial over 85% of infants were breastfed for longer than three months. By six months of age, HIV transmission was diagnosed in 33 children born to 180 women in the zidovudine group and 52 born to 175 women in the placebo group. The efficacy of zidovudine was thus estimated at 38% (95% confidence intervals 5% - 60%). There was no evidence of 'catch up' by the treated group during the period of breastfeeding up to 180 days. Data for children older (and breastfed for more) than six months are not yet available.

A further trial conducted in 260 women in Cd'Ivoire randomized women to receive either oral zidovudine 300mg twice a day from 36 weeks until the onset of labour or matching placebo²⁸³. At the onset of labour zidovudine 300mg was given every three hours until delivery versus placebo. In this trial population, over 95% of the infants were breastfed by their mothers and by three months of age 19 out of 115 babies in the zidovudine group were HIV infected compared with 30 out of 115 in the placebo group. This represents a relative risk of transmission of 0.63 (95% confidence intervals 0.38 - 1.06). The transmission risk at three months was similar to the transmission risk seen at four weeks also suggesting that breastfeeding had not produced a substantial narrowing of the difference between the two groups.

These results demonstrate that short-regimen of oral zidovudine appears to be safe and effective at reducing the risk of mother-to-infant HIV transmission. Of importance for many developing countries is that whether women do or do not breastfeed does not appear to make a substantial difference to the effectiveness of treatment. Other trials of reduced courses of ZDV alone are underway in Africa, and Haiti (see Table 3).

A reduction in the cost of zidovudine for developing countries has been announced by the manufacturers after negotiation with UNAIDS and in response to the results of the Thailand study²⁸⁴. This will assist in the implementation of these strategies. The World Health Organization has prepared guidelines for the use of antiretroviral drugs in developing countries²⁸⁵.

Combination therapy and other antiretroviral drugs

The UNAIDS co-ordinated PETRA trial uses a combination of ZDV and 3TC (lamivudine), and has been undertaken in predominantly breastfeeding populations in five sites in South Africa, the United Republic of Tanzania and Uganda. Long-term follow-up of the children is in progress but interim early efficacy results at six weeks of age of the infant have been reported. This trial compared the effectiveness of three different drug regimens with placebo. Arm A received zidovudine and 3TC from 36 weeks gestation, during labour and for one week postpartum to mother and child. Arm B received zidovudine and 3TC from the onset of labour and for one week postpartum to mother and child. Arm C received zidovudine and 3TC during labour only. Over 1790 women were recruited in all. The risk of transmission by six weeks of age in Arm A was 8.6%, in Arm B 10.8%, Arm C 17.7% and in the placebo group 17.2%. The study population continues to be followed up and the majority of women are breastfeeding²⁵⁴.

A recent French study, presented in abstract only, reported the use of 3TC (lamivudine) commencing at 32 weeks gestation in addition to the standard ACTG 076 zidovudine regimen²⁸⁶. Babies were treated with both drugs until six weeks of age. Two hundred women receiving this combination were compared with a cohort of 899 women receiving zidovudine alone. The rate of transmission in the combination group was 2.6% compared with 6.5% in the zidovudine group. This study was not a randomized trial and other factors may explain the decrease in transmission risk. One finding, however, was that two uninfected babies having received ZDV+ 3TC died of a neurological disorder due to a mitochondrial myopathy. This condition is rare and two neonatal deaths in 200 women suggest that 3TC or the drug combination may be responsible.

The use of non-nucleoside reverse transcriptase inhibitors (NNRTI) for the prevention of perinatal transmission is another possible approach. Nevirapine is a NNRTI with potent antiretroviral activity and a favourable safety profile but in which there is rapid development of drug resistance limiting the duration of its effect. Of particular interest is that the drug achieves high circulating levels which are long-lasting, raising the possibility of a one dose treatment in labour. Efficacy studies have commenced in South Africa and Uganda.

The use of combination antiretroviral therapy is becoming more common, with greater reductions in viral load. Recent recommendations for drug therapy for HIV advise the use of at least two agents, with the possible addition of a protease inhibitor^287,288,289 although rapid advances in the therapy of HIV infection means that such recommendations change frequently. Patients receiving this level of treatment may have undetectable viral loads. There has been little experience to date with the use of most of these drugs in pregnancy and many of the newer antiretroviral (ARV) drugs have not been fully evaluated for long-term effects on the infants. Table 4 shows the status of the USA's Food and Drug Administration (FDA) classification of the available antiretroviral drugs, while long-term animal toxicity studies and more experience in pregnant women are awaited. Phase I trials are completed or in progress for nevirapine, stavudine, didanosine, lamivudine, MKC-442 and the protease inhibitors¹¹¹. DMP-266 (Efavirenz, Sustiva) was shown to cause moderate to serious birth defects in monkeys, and may not be suitable for use in early pregnancy.

Table 4:FDA classifications of antiretroviral drugs for use in pregnancy^290,291

DRUG	FDA CATEGORY
NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITORS
Zidovudine (ZDV, AZT)	C
Zalcitabine (ddC)	C
Didanosine (ddl)	B
Stavudine (d4T)	C
Lamivudine (3TC)	C
NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITORS
Nevirapine	C
Delavirdene	C
PROTEASE INHIBITORS
Indinavir	C
Ritonavir	B
Saquinavir	B
Nelfinavir	B

Classification:

A: Adequate and well-controlled studies of pregnant women fail to demonstrate a risk to the fetus during the first trimester of pregnancy (and there is no evidence of risk during later trimesters)

B: Animal reproduction studies fail to demonstrate a risk to the fetus but well controlled studies of pregnant women have not been conducted

C: Safety in human pregnancy has not been determined, animal studies are either positive for fetal risk or have not been conducted, and the drug should not be used unless the potential benefit outweighs the potential risk to the fetus

D: Positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experiences, but the potential benefits from the use of the drug in pregnant women may be acceptable despite its potential risks

X: Studies in animals or reports of adverse reactions have indicated that the risk associated with the use of the drug for pregnant women clearly outweighs any possible benefit

Assuming favourable safety profiles, the use of combination therapy may be more effective in reducing mother-to-child transmission, by the greater reduction of viral load, and may be the most appropriate course in those countries where this is possible. However, cost and supply considerations will limit the availability of these drugs, and the issue of resistance development and the desirability of continuing therapy after pregnancy will have to be considered¹⁷⁹.

Immune therapy

Both passive immunization with hyper-immune HIV immunoglobulin (HIVIG) and active immunization with HIV vaccines have been proposed as alternative mechanisms to prevent mother-to-child transmission^111,113,292.

Passive immunization with intravenous HIV immunoglobulin has been investigated. A trial [ACTG185] of the use of HIVIG, in a cohort of women, who all received ZDV, was stopped after an interim analysis showed low transmission rates in both the study and control group. The transmission risk for the HIVIG Group was 4.1% (95% confidence interval 1.5%-6.7%) and the transmission risk for IVIG was 6.0% (95% confidence interval 2.8%-9.1%)²⁹³. Very large numbers would have been required to show any significant reduction in these rates attributable to the HIVIG use. Another study is ongoing in Uganda in ZDV na patients. Concerns remain about the costs and the donor sources for these products, standardized preparations and optimal delivery time.

Active immunization could possibly induce immunity in the mother and in the fetus by passive transfer of antibodies^111,294. Effective vaccines have not yet been identified, although several Phase I/II trials are in progress¹¹³.

Nutritional interventions

Following the finding that mothers with low serum levels of vitamin A were more likely to transmit HIV to their children¹⁹⁵, supplementation of vitamin A has been suggested as a preventive treatment. Several randomized controlled trials of vitamin A and other micronutrients are in progress (Table 3). The potential advantages of micronutrient supplementation would be the low price, possible other nutritional and health benefits for the mother and the fact that the intervention could be implemented simply without the need for HIV testing. Vitamin A deficiency has also been associated with increased viral loads in breast milk, and any reduction following supplementation would also be of benefit in breastfeeding women¹⁵⁹. Other micronutrients such as Zinc and Selenium have also been suggested as possible preventive agents.

A randomized controlled trial in the United Republic of Tanzania showed that multivitamin supplementation in HIV positive pregnant women decreased the risk of low birth weight by 44%, severe preterm birth (under 34 weeks gestation) by 39% and small size for gestational age at birth by 43%. Vitamin A supplementation had no effect on these variables. The multivitamin supplementation, but not vitamin A, resulted in significant increases in CD4+, CD8 and CD3 counts. The effect on mother-to-child transmission in this study has yet to be determined²⁹⁵. Preliminary reports from other vitamin A intervention trials suggest little benefit on transmission from vitamin A supplementation alone.

Mode of delivery

Caesarean section delivery has been associated with a reduction in transmission in a number of studies, although not in all^{119,181,207,223,296}. In some centres, Caesarean section has become a common mode of delivery for HIV positive women, despite the lack of conclusive evidence at the time. In 1995 in the United Kingdom, 44% of HIV positive mothers were delivered by Caesarean section²⁶².

A 1994 meta-analysis of prospective follow-up studies showed a small reduction in transmission with Caesarean section²²⁴. A more recent meta-analysis included five European and ten North American prospective studies totalling over 8500 mother-infant pairs. Elective Caesarean section reduced the risk of mother-to-child transmission by more than 50%, after adjusting for antiretroviral therapy, birth weight and maternal infection stage²⁹⁷.

A French study showed a transmission rate of 0.8% in women who had received long-course antiretroviral treatment and had an elective Caesarean section, compared to 6.6% with vaginal delivery²²⁸. A study in Switzerland reported no transmission in 45 women who received long-course ZDV and an elective Caesarean section²²⁷.

A randomized controlled trial of mode of delivery has been undertaken in Europe²²⁶. This trial randomized in excess of 400 women to elective Caesarean section delivery or expectation of vaginal delivery. Three out of 170 infants (1.8%) born to women in the Caesarean section group were HIV infected compared with 21 out of 200 (10.5%) born to women in the vaginal delivery group. A treatment effect odds ratio of 0.2 (95% confidence intervals 0.1-0.6).

Two thirds of the women taking part in this trial were exposed to zidovudine during pregnancy. In this sub-group 0.8% of babies born to the women allocated to Caesarean section were HIV infected compared with 4.3% of those born to women allocated vaginal delivery. This gives an odds ratio of 0.2 with 95% confidence intervals of 0-1.7. For women not exposed to zidovudine during pregnancy the odds ratio for transmission was also 0.2 suggesting that the protective effect of Caesarean section persists whether women were or were not prescribed zidovudine during pregnancy.

In addition there were no serious adverse complications in either group. Postpartum fever was reported more commonly in women delivered by Caesarean section although the overall incidence was low.

The use of Caesarean section must take into account the possibility of maternal morbidity and mortality^109,110,298, the availability of safe operating facilities, the potential increased service commitments and the accessibility of maternity services for women in future pregnancies.

Vaginal cleansing

The use of antiseptic or antiviral agents to cleanse the birth canal during labour and delivery has been hypothesized as a possible approach to reducing intrapartum transmission of HIV-1. The use of chlorhexidine lavage to reduce the transmission of group B streptococci was demonstrated in Scandinavian studies²⁹⁹. The concept is attractive for HIV prevention, as it would be an inexpensive intervention, readily achievable in most health care settings, would not require identification of HIV-infected women prior to the intervention and could have other health benefits.

A Malawian quasi-randomized study compared four-hourly aqueous chlorhexidine 0.25% solution by vaginal swabbing after vaginal examinations and a chlorhexidine wash for the baby, with a control group receiving no wash. No overall reduction was shown in the rate of HIV transmission in the study group, however, only 60% of infants were followed up. There was a significant reduction in transmission in mothers who had ruptured membranes for more than four hours²²². Most deliveries in this trial occurred within a short time of the vaginal swabbing procedure. Significant reductions in neonatal and puerperal sepsis were also seen following this intervention³⁰⁰ and use of this procedure may be advantageous for these other health benefits, in addition to any possible role in prevention of mother-to-child transmission of HIV³⁰¹.

Benzalkonium Chloride has been suggested as an alternative antiseptic agent for vaginal lavage, utilizing the antiseptic from 36 weeks gestation in an attempt to maximize the possible benefit (Table 3). The intervention of vaginal cleansing remains a feasible option for resource poor settings and further research work should be undertaken on different concentrations or formulations of agents and methods of application to determine whether the efficacy can be improved.

Modification of infant feeding practice

The increased risk of HIV transmission through breastfeeding is well documented^{237,238,302,303}. Breastfeeding is responsible for a high proportion of mother-to-child transmission in developing countries, where 1 in 7 children born to HIV-positive mother will be infected through breast milk²⁴⁷. Breastfeeding may double the transmission rate^111,238,304 and may be the major determinant for the difference in transmission rates between developed and developing countries. A meta-analysis of studies of transmission through breastfeeding showed the additional risk of transmission through breastfeeding to be between 7 and 22%, and close to 30% for women who are infected during the breastfeeding period²³⁷. Potential modifications of infant feeding practices include complete avoidance of breastfeeding, early cessation, pasteurisation of breast milk, and avoiding breastfeeding in the presence of breast abscesses or cracked nipples^111,305.

The debate on appropriate infant feeding has focused almost exclusively on the risks and benefits of breastfeeding for the infant. Maternal considerations should also be taken into account, although there is a need for further research into the relationship between HIV infection, nutritional status and immune function in breastfeeding mothers. The concerns about the effect of breastfeeding on maternal health in HIV positive women include the potential effects of breastfeeding and resultant weight loss on the immunity and long-term prognosis of the mother. The effects of advanced disease or nutritional deficiencies on the risk of transmission in breast milk and the function of immunologically active components of breast milk from severely immune suppressed or malnourished mothers also need to be considered³⁰⁶. Breast milk could have advantages for those infants already infected with HIV by the time of birth, if there was a way to identify these children.

In developed countries, few HIV positive women will breastfeed³⁰⁷. In resource poor settings, alternatives to breastfeeding may not be feasible for financial, logistical and cultural reasons^126,308,309. Mothers should be given the information on the advantages and disadvantages of breastfeeding and replacement feeding with regard to HIV infection, and encouraged to make a fully informed decision about infant feeding. They should be supported in their decision²⁴⁷.

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Voluntary HIV counselling and testing in pregnancy

Testing of antenatal women

Pregnant women have been the target of many seroprevalence studies, as they provide an accessible cohort for HIV testing and a stable sampling frame^{19,23,22,310,311}. While valuable information has been obtained on trends in the epidemic, the practice of testing in pregnancy has been criticized in the past, as one which stigmatizes women and which has not led to implementation of appropriate health strategies^312,313.

With increasing knowledge about HIV and about mother-to-child transmission in particular, the focus has moved from the possible public health benefits of testing in pregnancy to the potential benefits for the individual woman^314,315. This has re-emphasized the need for the provision of appropriate facilities for testing and counselling^{126,277,316,317,318,319,320,321,322,323,324}. Voluntary testing of pregnant women is recommended and offered in many countries^{17,325,326,327}. The introduction of testing programmes has increased the number of identified HIV positive women in many centres³²⁸. Despite this, identification of infected women may not be optimal if women do not access antenatal care, or where counselling and testing services are inadequate^{262,327,329,330,331,332,333}.

Wherever possible, voluntary counselling and testing should be available to any pregnant woman who requests it and offered to all in areas of moderate or high prevalence. Routine testing of pregnant women without consent or without access to counselling is, however, an unacceptable practice and the disadvantages may negate any benefit obtained from knowing the HIV status of the women. These include a reluctance to utilize maternity services through fear of discrimination, denial of a positive diagnosis and stigmatization. Recent discussion about, and recommendations for mandatory testing of pregnant women or newborns have led to concern about the autonomy and rights of women^315,329.

There are, however, a number of potential benefits to women of voluntary HIV testing prior to or during pregnancy. This is the case even in the absence of expensive interventions such as long-course antiretroviral therapy. These benefits include:

1 Where a woman is found to be infected, this knowledge can facilitate early counselling and treatment.

2 A diagnosis in the mother allows appropriate treatment and follow-up of her child.

3 Knowledge of her HIV status enables the woman to take decisions on continuation of the pregnancy and on future fertility.

4 Testing allows an opportunity to implement strategies to attempt to prevent transmission to the child.

5 Knowledge of HIV status enables the woman to take precautions to help prevent transmission to sexual partners.

6 Women diagnosed as HIV positive can tell their sexual partners and enable partners to be counselled and tested.

7 If the test result is negative, women can be guided in appropriate HIV prevention measures and risk reduction behaviour.

Balanced against these advantages are the possible disadvantages of HIV testing in pregnancy. These will vary from community to community, but reports have described an increase in the risk of violence against women; the possibility that the woman may be stigmatized within her community and by health workers; higher levels of anxiety and psychological sequelae; and concerns about the additional work load for maternity services^{334,335,336,337}. Several studies have described the reluctance of some women to return for their test results³³⁷,³³⁸'³³⁹. In Nairobi, 5.9% of HIV-positive women reported violence related to the HIV test result. After changing to a policy of giving results out only on request, only 35% of women who had agreed to testing returned to ask for results³³⁷. In Kigali, 63.9% of positive women and 71.3% of HIV-negative women returned for test results and the only variable found to be associated with failure to return for counselling was a positive HIV test³³⁸.

Women should be encouraged to bring their sexual partner(s) for counselling and testing wherever possible. However, very few testing services have managed to achieve much success in this regard^336,338. The best predictor of return for counselling by women in one US study was the time spent in counselling women and the counsellor's skills³³⁹. Voluntary counselling and testing (VCT) services for couples, preconceptual counselling and testing services not linked to antenatal care may increase testing uptake. However, it must be emphasized that, unless people have real choices for action once they have their test results (i.e. access to affordable services such as mother-to-child transmission preventive interventions, and care and support services), there is no good reason to take a test (see: Counselling and voluntary HIV testing for pregnant women in high HIV prevalence countries: Guidance for service providers (UNAIDS, May 1999))

A qualified person should take the blood specimen for an HIV test, using "universal precautions" against accidental transmission in all cases. These must include the safe disposal of needles and syringes. The type of tests used will depend upon local seroprevalence, policy and available facilities. In most cases blood specimens will be sent to the appropriate laboratory, but in some areas, dry blood spot testing may be an acceptable alternative. The first line test for HIV-antibodies is an enzyme-linked immuno-absorbent assay (ELISA) test, or a rapid test algorithm. Depending on local conditions, a confirmatory test with a second ELISA or rapid test using a different test kit, or a Western Blot should be performed. Any testing strategy must be undertaken with appropriate laboratory quality assessment³⁴⁰,³⁴¹.

With increasingly sensitive and specific simple and "rapid" tests becoming available, on-site testing may become more feasible (see The importance of simple/rapid assays in HIV testing. WHO/UNAIDS recommendations; WER 1998, 73, 321-328). Recent reports of the use of "same-day" rapid test results in a rural hospital in a resource-poor setting and in an urban STI clinic have suggested that this is an acceptable and appropriate intervention³⁴²,³⁴³. Preliminary reports of the use of dual rapid tests for same day diagnosis in antenatal clinics suggest that this is an appropriate and acceptable way to provide testing in this setting. The major advantage is that early results enable more women to access antenatal strategies for the prevention of mother-to-child transmission.

Counselling before and after HIV testing in pregnancy

Pre- and post-test counselling are essential elements of the management of HIV in pregnancy. Pre-test counselling enables women and men to make informed decisions about an HIV test. Post-test counselling is an integral part of the management of the HIV-positive person, and provides an important opportunity for risk-reduction messages for those found to be HIV-negative.

Pre-test counselling

HIV testing should be accompanied by the provision of pre-test information and by informed consent to the test by the woman (see Table 5). Pre-test counselling implies explanation of both the test and the illness to the woman in a non-directive manner, and answering any questions prior to the performance of the test. The woman should be given time to decide on the test and, if unsure, should be counselled to take more time to think about the test and return at a later stage. Information about HIV testing can be incorporated into the health education and promotion activities of antenatal clinics and need not be too time consuming within maternity services³¹⁹. Various models have been tried, including group counselling, video education, incorporating information on HIV into the first visit interview by midwives and the use of lay counsellors^344,345. An appropriate model should be developed for the circumstances of each service, based on the prevalence and the level of prior awareness of the women in the community.

Table 5 : Pre-test counselling
[Based on guidelines from the Johannesburg Community AIDS Centre]

Take client to private setting for counselling Assure the client of confidentiality Explain or determine the reasons for HIV testing Elicit information about the person's current and previous risk behaviour in a sensitive manner Provide information about HIV and AIDS Provide information about the HIV antibody test, including information about the "window period" of infection Review the implications of a positive test result for the client Discuss the person's possible responses to a positive test result Discuss the implications of a negative test result Provide information about test procedures Obtain informed consent

Post-test counselling

The essential elements of post test counselling for HIV positive women are illustrated in Table 6. Counselling implies more than merely giving a positive result, and continued care and advice will be necessary as part of the management throughout the pregnancy and beyond^344,346,347. The choice of appropriate counsellor will depend upon the circumstance of the practice or health service: counsellors ideally should have personal qualities, which equip them for the job, but many of the skills can be acquired during training. Wherever possible, counselling should be provided in the woman's home language and within the same cultural background. The involvement of peer counsellors - women who are themselves HIV-infected, who are able to counsel and to share their own experiences, fears and successes may be very valuable and should be encouraged. The integration of peer counsellors and support groups into the work of health services can be a very valuable addition to the available services.

Table 6 : Post-test counselling
[Based on guidelines from the Johannesburg Community AIDS Centre]

See the client personally to give result - no telephonic results, preferably not before a weekend Give the result as soon as possible after the test is done Inform the client of the test result Deal with the feelings arising from a negative result and explore prevention of infection and the window period Deal with the feelings arising from a positive result Identify the person's immediate concerns Discuss how the client plans to spend the next few hours and days Identify what support the client has Discuss who the client may want to tell about the result and risks to sexual partners Identify what difficulties or problems the client foresees and how to deal with them Encourage the client to ask questions Provide information on a healthy lifestyle, medical follow-up, local support systems Refer for follow-up care and counselling

The delay between taking the test and giving the result should be as short as possible, as the woman may be very concerned about the test and the implications of the result. Women who test positive should be encouraged to bring their male partner(s) for counselling and testing wherever possible.

Post-test counselling should also be provided for HIV-negative women, with a focus on providing information to enable them to avoid infection. This could be provided on a group basis, or by individual health workers, depending on the circumstances.

Counselling about pregnancy-related issues

There are several issues to be addressed when counselling HIV positive pregnant women, in addition to the general issues related to HIV infection. These include information about the interactions of HIV and pregnancy, options of termination of pregnancy, discussion about disclosure to the male partner, the risk of mother-to-child transmission and possible interventions to prevent this, other treatment options, infant feeding and HIV and future fertility. Some of these pregnancy-related issues are detailed in Table 7.

Table 7 : Issues in counselling HIV-positive pregnant women

The effect of pregnancy on HIV infection The effect of HIV infection on pregnancy outcome: risks of adverse pregnancy events The risk of transmission to the fetus during pregnancy, delivery and breastfeeding Termination of pregnancy options Treatment options during pregnancy Interventions available to attempt to prevent mother-to-child transmission Infant feeding options: the advantages and disadvantages of breastfeeding Disclosure of results to male partners and/or to other significant family or community members: advantages and risks The need for follow-up of both mother and child Future fertility and contraceptive options

HIV-infected women should be given appropriate information to make informed decisions about the continuation of their pregnancy and future fertility³⁴⁸. Termination of pregnancy should be offered to HIV positive women; where this is legal. It should be clear to health care workers that offering termination should never be coercive and that all women, irrespective of their HIV status, have the right to determine the course of their reproductive life. Although there are some reports of increased rates of termination in HIV positive women, the majority of women will elect to continue with the pregnancy^{249,349,350,351}. Knowledge of HIV infection had little effect on reproductive trends and the decision on future children in a number of studies^{248,352,353,354} although this has been seen more in developing countries than developed countries. However, a family planning intervention in Rwanda, providing access to and information about contraceptives, showed a reduction in subsequent pregnancies which was greater than in HIV-negative women³⁵⁵, and other studies have shown a reduction in the number of pregnancies in HIV positive women^{349,356,357,358}.

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The management of HIV positive women during pregnancy is multifaceted, combining medical and obstetrical management with counselling and social support. The woman's social and psychological concerns may be as important as her need for medical care. Ideally, a team approach with health workers, counsellors and support groups should be used^{358,359,360,361,362}.

In all cases, the management in pregnancy, including antiretroviral treatment, should be seen as only a part of the continuum of care for the mother and child^{360,363,364,290}. Ongoing care may be undertaken at home, within the primary health care services, at hospitals, or at specialist clinics, depending upon the individual needs and available facilities³⁶⁵. The following discussion highlights some of the management issues for HIV positive pregnant women, and does not provide detailed guidelines. Diagnostic procedures and medical management will be dependent upon the available resources and each country should develop appropriate recommendations for their own situation.

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Most HIV positive women will be asymptomatic and have no major obstetrical problems during their pregnancies^{99,366,367,368,369}. They should receive similar obstetric antenatal care to that given to HIV-negative women, unless indicated by the need to provide specific HIV-related treatment. There is no evidence that there is a need to increase the number of antenatal visits, provided there are no complications of the HIV infection, although additional counselling time may be required. The care of the HIV positive woman during pregnancy should include ongoing counselling and support as an integral part of the management. Advice on the possible risks of unprotected intercourse during pregnancy should be provided.

Obstetrical management

Antenatal care of the HIV positive pregnant woman will depend on the woman's risk of experiencing an adverse perinatal outcome. To an extent this will be mediated by other obstetric risk factors and antenatal care will need to be tailored to the individual woman. Consideration can be given to the assessment of fetal growth, whether by regular uterine fundal height measurements or, where available, by serial ultrasound assessments.

Invasive diagnostic procedures, such as chorion villus sampling, amniocentesis or cordocentesis should be avoided where possible, due to a possible risk of infection of the fetus³⁰². External cephalic version of a breech fetus may be associated with potential maternal-fetal circulation leaks and the advantages and disadvantages of the procedure should be very carefully considered.

Examination and investigations

HIV positive women should have a full physical examination at the first visit. Particular attention should be paid to any signs of HIV-related infections [particularly tuberculosis], oral or vaginal thrush, or lymphadenopathy. Herpes zoster [shingles] in a young woman is often an early sign of HIV infection and current herpes lesions or the scars from previous infection may be found. Other co-existent sexually transmitted infections, especially syphilis, are common in HIV positive women^{96,97,370,371} and may increase the risk of transmission and the level of virus in vaginal and cervical secretions. Clinical diagnosis and treatment of vaginal or cervical inflammation, abnormal discharge or STI should be a priority. The pregnant woman should be monitored for any signs of HIV-related opportunistic infections and for any other intercurrent infections, such as urinary or respiratory infection. Maternal weight should be monitored and nutritional supplementation advised where necessary. The oro-pharynx should be examined at each visit, for the presence of thrush.

Laboratory investigations will depend upon the available resources of the health service. Syphilis testing should be undertaken, and repeat testing in late pregnancy may be advisable⁴⁰. A haemoglobin estimation is mandatory and a complete blood count should be performed and T cell subset investigations undertaken where possible. Anaemia is more common in HIV-infected women and repeated haemoglobin tests may be helpful. Viral load estimation may provide a valuable prognostic indicator, where available. A cervical smear should be performed if this has not been undertaken within the recent past. Colposcopy should be reserved for women who have an abnormal cervical smear result.

Medical treatment during pregnancy

The medical care of HIV positive women should be tailored to the individual needs of the woman. In general, pregnancy is not a contraindication for the most appropriate antiretroviral therapy for a woman or for most of the medical management of HIV-related conditions, but the risk to the fetus should always be considered, and treatment modified if necessary²⁹⁰.

The value of vitamin A supplementation in reducing transmission has not been proven, but multivitamins may provide cost effective nutritional support^372,373,374. Mebendazole should be given at the first visit in areas of high hookworm prevalence.

Malaria in pregnancy causes high maternal and infant morbidity and mortality, and may be associated with increased risk of mother-to-child transmission of HIV^216.217. Current recommendations are that intermittent treatment with an effective, preferably one-dose antimalarial drug should be made available to all primigravidae and secundigravidae in highly endemic areas. This should be started from the second trimester and given at intervals of not more than one month apart.

Prophylaxis for opportunistic infections should be given in pregnancy, as indicated by the clinical stage of the HIV infection, and according to local policy. Prophylaxis and treatment for tuberculosis should be given where indicated, although streptomycin and pyrazinamide are not recommended during pregnancy. Pneumocystis carinii pneumonia (PCP) prophylaxis should continue through pregnancy: sulfamethoxazole/trimethoprim (Bactrim/Septran) or pentamidine can be used. The risk to the fetus of maternal sulphonamide administration in the third trimester is outweighed by the risk to maternal health of PCP and kernicterus has not been reported where the drug was not also used in the neonatal period⁵. Consideration should be given to pneumococcal and Hepatitis B vaccination.

Treatment for opportunistic infections during pregnancy depends on the clinical stage of the patient. Treatment regimens should follow local policy guidelines. Where a variety of treatment options are available, those with the lowest risk to the fetus should be used. Dermatological conditions are common in HIV positive women and men, and treatment may be required for prolonged periods. Acyclovir can be used safely after the first trimester. Topical imidazole antifungals or topical gentian violet can be used throughout pregnancy and oral fluconazole can be used after the first trimester, if required.

Antiretroviral therapy

The use of antiretroviral drugs in pregnancy should be considered for two indications: the health of the mother and prevention of transmission^364,290,291. Pregnancy should not be a contra-indication for antiretroviral therapy in the mother, if indicated. The use of ZDV in the prevention of transmission to the fetus has been discussed above^375,376,377. Current recommendations for adult antiretroviral therapy are that monotherapy with ZDV is sub-optimal treatment and that two antiretrovirals with the possible addition of a protease inhibitor is preferable^{288,289,378,379}. Although there is a theoretical risk to the fetus from combination therapy, there is limited experience with the use of other antiretrovirals such as lamivudine, stavudine, and protease inhibitors in pregnancy. Some have recommended stopping these therapies during the first trimester and restarting the combinations, but this also carries a risk of developing resistance. Detailed recommendations have been released in the USA on combination therapy in pregnancy²⁹¹. As many of the newer compounds do not have long-term safety data following use in pregnancy, this should be discussed with the patients. The use of any antiretroviral drugs should be accompanied by an explanation of the available knowledge to the women and advice that there should be long-term follow-up of the child²⁷².

Care during labour and delivery

Care during labour for HIV positive women should follow routine practice in most respects. Prolonged rupture of membranes should be avoided, as mother-to-child transmission is increased where membranes are ruptured for more than four hours¹¹⁹. Artificial rupture of membranes should not be undertaken if progress of labour is adequate. Given these advantages, this may be introduced as a routine part of the management of labour for all women in high prevalence areas.

There are conflicting reports of the importance of obstetric interventions in the facilitation of transmission^111,113. As a general rule, any procedure which breaks the baby's skin or increases the baby's contact with the mother's blood - such as scalp electrodes or scalp blood sampling - should be avoided unless absolutely necessary, due to the unconfirmed magnitude of the risk of these for HIV transmission. Universal precautions should be applied in managing labouring women in all cases. Episiotomy should not be performed routinely, but reserved for those cases with an obstetrical indication.

If an assisted delivery is required, forceps may be preferable to vacuum extraction, given the risk of micro-lacerations of the scalp from the vacuum cup. There is increasing evidence that elective Caesarean section may help prevent transmission of HIV to the baby²²⁵. The operation carries risks of maternal complications and is associated with higher post operative morbidity in HIV positive women¹¹⁰. The decision on Caesarean section delivery should be made on an individual basis, taking into account the available facilities, and will not be possible in most developing countries with high HIV prevalence. Prophylactic antibiotics should be given for both elective and emergency Caesarean sections.

Postpartum care

The postpartum care of HIV positive women should be similar to that for uninfected patients. They do not require separate nursing facilities. Women may, however, require private facilities to lessen the social stigma associated with not breastfeeding if this is the choice they make in a culture which is likely to condemn such behaviour.

HIV positive women are more prone to postpartum infectious complications – including urinary tract, chest, episiotomy and Caesarean section wound infections. Health workers should be aware of this and observe for signs of infection. Mothers should be given information on the early symptoms of infection at the time of discharge, especially where the postpartum hospital stay is short. All mothers should be given instructions on perineal care and the safe handling of lochia and blood stained sanitary pads or materials.

Mothers should be given information on how to care for their babies without the risk of exposure to infection, and full discussion on the risks and benefits of infant feeding choices. If, after counselling, the mother chooses not to breastfeed, she should receive full information on adequate replacement feeding up to two years of age, and guidance on breast care, until lactation stops. Mothers who choose to breastfeed should be advised of the possible increased transmission risk in the presence of cracked nipples, mastitis, breast abscess or of oral lesions in the child and should be taught how to prevent such problems through adequate breastfeeding techniques. Reduced duration of breastfeeding and early cessation may be encouraged to reduce the risk of transmission where this can be achieved safely. The mother should be counselled on the need for follow-up care for her and her child, and the available options for testing of the child. She should be given information about and referred to local HIV support groups. Contraceptive advice should be given and early arrangements made to start with an appropriate method. Contraceptive advice is particularly important when a mother does not breastfeed because of the loss of the contraceptive properties of breastfeeding^380,381.

Care of neonates

Babies of HIV positive mothers should be handled with gloves until maternal blood and secretions are washed off, after which time they can be handled safely by mothers and health workers. Anaemia has been the most common complication seen in the neonate with the long-course treatment of six weeks ZDV to the child. Haemoglobin should be measured at baseline and after six weeks and 12 weeks if this regimen is used. The anaemia risk is much less with the short-regimen. Infants receiving long-course antiretrovirals may experience a transient elevation of hepatic transaminases.

There is less experience with the use of combination therapy in the pregnant mother and the risk of toxicity to these infants, and more intensive haematological monitoring would be advised.

Mothers should decide on infant feeding practice before delivery and be supported in their choice. Children should be referred for long-term follow-up and for repeat testing for diagnosis of HIV infection, either by early PCR if available, or by ELISA at 15 to 18 months.

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(See Guidance Module on Antiretroviral Treatments, Module 7. Treatments following exposure to HIV)

Exposure to blood and other body fluids is common in obstetric practice^{382,383,384,385,386} and staff should receive information, training and access to equipment in order to protect themselves³⁸⁷. In areas of highest HIV prevalence, tests may not be available and many women will also be in the "window period" before seroconversion, and may not be identified by routine HIV-antibody tests. Lack of access to nosocomial infection prevention measures may unfortunately be common in these countries^388,389,390. A study of occupational exposure in the United Republic of Tanzania showed that health workers were exposed on average to five sharp injuries and nine splashed exposures each year, with a higher risk in surgeons³⁹¹. In Rwanda, no evidence was found for any HIV infection caused by occupational blood contact in 215 traditional birth attendants, exposed to an estimated 2234 potentially infectious blood-skin contacts over five years³⁹².

All patients should be regarded as potentially infectious, not only for HIV, but also for Hepatitis and other pathogens^393,394. Health care workers must ensure that they use universal precautions against accidental infection at all times. These require the provision within health services of protective devices and clothing and access to safe containers for sharp instruments³⁹⁵.

Universal precautions

The best protection against occupational exposure to pathogens is the use of universal (or standard) precautions in all cases.

Important precautions in obstetrics include:

1 Reducing needlestick injuries by handling used needles as little as possible, using a needle holder during episiotomy, avoiding recapping disposable needles and taking great care in recapping blood sampling barrel system needles or non disposable syringes, placing needles and other sharps in the appropriate containers

2 Washing hands with soap and water immediately after contact with blood or body fluids

3 Wearing suitable gloves when expecting exposure to blood or body fluids

4 Covering broken skin or open wounds with watertight dressings

5 Wearing an impermeable plastic apron for delivery

6 Wearing eye shield for operating or assisting at Caesarean Section, and for suturing episiotomies

7 Wearing double gloves, if possible, for all operations, which reduce considerably the amount of blood carried through if a glove is punctured

8 Using an appropriate sized needle (21 gauge, 4 cm, curved) for the repair of episiotomy, together with a technique using a needle holder

9 Passing all sharp instruments onto a receiver, rather than hand-to-hand at
Caesarean section and modifying surgical practice to use needle holders and to avoid using fingers in needle placement

10 Using long-cuffed gloves for manual removal of a placenta

11 Wherever possible, avoiding the need for suction of newborns and using wall suction or a suction machine when suction is required. Suction pressure should be less than 140 mm Hg to avoid damage to the neonate. If no other suction is available, ensuring that the trap in the mouth operated De Lee suction apparatus is functional

12 Disposing of solid waste such as blood soaked dressings or placentas safely

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Needlestick injuries occur relatively commonly in obstetric practice and health workers should know their local policy for the appropriate management of injury. The most common form of injury occurs when re-sheathing needles. Injuries from hollow needles are more dangerous than those from solid surgical needles, as they are more likely to transfer blood.

Any such injury carries a risk of exposure to HIV, Hepatitis virus, and other pathogens. For Hepatitis B the risk of infection is between 5% (HBV-e Ag negative source patient) and 43% (HBV-e Ag positive source patient). The amount of blood required to transmit Hepatitis B is only 0.00004 ml, while a minimum of 0.1 ml is required for HIV transmission. All health care workers should have Hepatitis B vaccinations, in view of the high risk of accidental transmission, and high prevalence in many developing countries.

Estimates of the risk of HIV transmission from patient to health care worker vary from 0.23% to 0.5% per exposure^{384,396,397,398,399}. The type of exposure and the stage of the HIV positive source patient affect the risk, since the viral load will be greater in the recently infected patient and in late stages of the disease. The estimated risk of transmission of HIV from a deep needlestick injury from an HIV-positive patient is 0.4%, and the estimated risk of transmission from a trans-cutaneous exposure is 0.05%.

Management of needlestick injuries and other accidental blood exposure

There is evidence that the risk of infection is reduced by the use of post exposure prophylaxis with anti-retroviral drugs, by as much as 79%⁴⁰⁰. The management of needlestick injuries should be according to local guidelines and antiretroviral drugs should be used for significant injury, if available in the country. Recent guidelines have set out recommendations for the use of antiretrovirals in these cases ^{379, 401, 402, 403, 404, 405}.

First aid treatment

First aid measures should be undertaken as soon as possible after injury. These should include decontamination of the exposure site as soon as possible, allowing a needlestick injury or cut to bleed, washing the area with chlorhexidine or other antiseptic and decontaminating exposed mucosa or conjunctivae by vigorous flushing with water.

Assessment of risk following exposure

A clinical assessment should be made about the level of risk following exposure. This is based upon the following factors:

A. THE NATURE OF THE INJURY:

Puncture: type of needle [hollow or solid] depth of penetration volume of blood thought to have been injected Laceration Mucosal contamination Contamination of non intact skin Bite

B. THE SOURCE OF EXPOSURE:

Blood, blood products, body fluids, amniotic fluid, semen and vaginal secretions are associated with transmission of HIV, while stool and urine are not

C. THE SOURCE PATIENT:

Clinical condition or available laboratory results such as viral load

Counselling and testing of the source patient

HIV testing should be offered to all source patients, with their informed consent. Where such consent is not available (for example in a comatose or anaesthetized patient), this consent should be obtained from a relative or senior medical staff member. Where the source patient does not wish to know the HIV result, it may be acceptable to offer to take blood for the test (for the protection of the health care worker), without disclosing the result to the source patient. In practice, very few patients refuse consent and most are extremely concerned about health worker risk.

Counselling and testing of the health worker

A baseline HIV test is required for the management of the health worker and in case of a later claim for compensation. If the health worker has not been immunized for Hepatitis B, a test for HBV should also be undertaken at this time.

Follow-up tests should be done at six weeks, three months and six months. PCR testing may provide an earlier result, if available, which can reduce the stress of waiting for many months for a test result for seroconversion.

The injured staff member should receive follow-up counselling at any stage during the six months that this is required. Counselling should include advice to practise safe sex, to avoid blood donation and to consider delaying pregnancy for six months, if this had been planned.

Post exposure prophylaxis

Post-exposure drug prophylaxis should take into account the type and source of the injury and is not recommended for superficial needlestick injuries or cutaneous exposure. For deeper injuries or lacerations, the use of post exposure prophylaxis should be considered, and treatment started as soon as possible after the injury, with the first dose of ZDV ideally taken within two hours⁴⁰².

Combination therapy, such as ZDV and 3TC (lamivudine), is currently recommended^402,403,404. The addition of a protease inhibitor is recommended for deep exposures in the guidelines of Canada and the USA^402,403. Where viral drug resistance is less common, this may not be as necessary. The decision to use post exposure prophylaxis must be taken by the injured party, after discussion of the benefits and risks.

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