HIV infection is associated with high morbidity and mortality. Effective treatment with a combination of three or more anti-retroviral drugs, known as highly active anti-retroviral therapy (HAART),has the capacity to prolong greatly the quality and length of life. British HIV Association guidelines regarding the treatment of HIV infection and HAART regimens used are available from the website: www.aidsmap.com. In the UK, it is estimated that 49 500 adults are infected with HIV, of whom one-third are unaware of their diagnosis. Among adults newly diagnosed with HIV in the UK, 58% are thought to have acquired their infection through heterosexual exposure, of whom the majority are of black African ethnicity and who were probably infected in sub-Saharan Africa. The incidence of heterosexually acquired HIV infection in the UK is rising steadily. Life expectancy is increased as a result of HAART. These factors have led to an increase in the prevalence of pregnant women who are HIV positive in the UK. The Unlinked Anonymous Prevalence Monitoring Programme was introduced in 1990 to assess the prevalence of HIV infection, both diagnosed and undiagnosed, in accessible groups of the adult population. Data from this programme showed that, in 2002, there were an estimated 686 births to HIV-positive women in the UK, with over 60% of these in London. The prevalence of HIV infection in women giving birth in London was 0.38%, compared with 0.06% in both the rest of England and in Scotland.
The risk of mother-to-child transmission of HIV varies between 15% and 20% in non-breastfeeding women in Europe and between 25% and 40% in breastfeeding African populations. Mother-to-child transmission of HIV is largely preventable where universal antenatal HIV screening is undertaken, exclusive artificial formula feeding is feasible and where there is the provision for anti-retroviral therapy and delivery by caesarean section. The principal risks of transmission are related to maternal plasma viral load, obstetric factors and infant feeding.
It is well established that advanced maternal HIV disease, low antenatal CD4 T-lymphocyte counts and high maternal plasma viral loads are associated with an increased risk of mother-to-child transmission. The latter is now recognised as being the strongest predictor of transmission. Two large studies demonstrated that perinatal transmission was significantly associated with maternal plasma viral load. These studies also showed that no transmission occurred where maternal plasma viral load was less than 1000 copies/ml (0/57)4 and less than 500 copies/ml (0/84). However, a meta-analysis of seven prospective studies demonstrated 44 cases of perinatal HIV transmission among 1202 women with plasma viral loads of less than 1000 copies/ml at or near the time of delivery. These data suggest that, at present, there is insufficient evidence for a plasma viral load threshold below which transmission never occurs. Current plasma viral load assays have lower limits of detection than those used in the above studies (as low as 50 copies/ml). In women who do not breastfeed, it is estimated that, in the absence of intervention, over 80% of HIV transmissions from mother to child occur late in the third trimester (from 36 weeks), during labour and at delivery, with fewer than 2% of transmissions occurring during the first and second trimesters. The principal obstetric risk factors for mother-to-child HIV transmission are vaginal delivery, duration of membrane rupture, chorioamnionitis and preterm delivery.
Breastfeeding is associated with a two-fold increase in the rate of HIV transmission. UK data obtained at a time when HAART was not yet available suggest that pregnant women who are HIV positive who breastfeed their baby increase the risk of mother-to-child transmission from approximately 14% to 28%.
Observational studies from North America and Europe suggest that, in women without advanced HIV disease, there is no increased risk of accelerated immnosuppression in pregnancy, although CD4 Tlymphocyte counts fall during pregnancy and return to prepregnancy levels postpartum. This guideline relates to the management of HIV in pregnancy in developed countries, as it was considered beyond the scope of a single guideline to address management in both developed and developing country settings.
This guideline can be downloaded as a pdf using the link below.
A Russian language translation of this guideline is also available:
