|HIV in Pregnancy: A Review (UNAIDS, 1999, 67 p.)|
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.