[HIV-1 transmission from mother to child and its prevention]

Mother-to-child transmission of HIV-1 can occur during pregnancy, labor/delivery, or breastfeeding. Without intervention HIV infection occurs in about 35% of infants born to HIV-infected women: 10% during pregnancy, 15% during labor/delivery, and 10% during breastfeeding. As early as 1994, the PACTG 076-ANRS 024 study documented the remarkable effectiveness of AZT in reducing mother-to-child HIV transmission from 26% to 8% in women who did not breastfeed. Since then, AZT or multiple antiretroviral therapies has been widely used in pregnant HIV-infected women in industrialized countries resulting in decline of the transmission rate to less than 3%. In developing countries where most perinatal transmissions occur, preventive treatment is more difficult to implement. Abbreviated treatment using AZT or nevirapine (NVP) in a single dose to the mother during delivery and to the newborn reduces perinatal transmission but to a lesser extent in comparison with standard treatment. Combination treatment using AZT + 3TC or AZT + NVP is more effective. Elective cesarean section has also been proposed but is not recommended in developing countries. To date the only alternative of proven efficacy for reducing transmission during breastfeeding is formula feeding, but this method may be hazardous if sanitary conditions are poor. Studies are currently under way to test the efficacy of antiretrovirals administered to the mother and/or infant in reducing HIV transmission during breastfeeding.