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close this bookHIV in Pregnancy: A Review (UNAIDS, 1999, 67 p.)
close this folderSECTION A : HIV IN PREGNANCY
View the document(introduction...)
View the documentEpidemiology of HIV
Open this folder and view contentsSusceptibility of women to HIV infection
View the documentEffect of pregnancy on the natural history of HIV infection
View the documentEffect of HIV infection on pregnancy
Open this folder and view contentsMother-to-child transmission
View the documentInterventions to prevent mother-to-child transmission of HIV
Open this folder and view contentsAppropriate interventions to reduce mother-to-child transmission
Open this folder and view contentsVoluntary HIV counselling and testing 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 transmission4,10,11.

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 sites1, 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 communities22, 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.