This Committee Opinion is being revised to provide updated guidance on the management of pregnant women during pregnancy and delivery to prevent mother-to-child transmission of the human immunodeficiency virus (HIV). Prevention of transmission of HIV from the woman to her fetus or newborn is a major goal in the care of pregnant women infected with HIV. Continuing research into mother-to-child transmission of HIV has suggested that a substantial number of cases of perinatal HIV transmission occur as the result of fetal exposure to the virus during labor and delivery. The precise mechanisms are not known. Established and ongoing research has shown that treatment of HIV-infected pregnant women with combined antiretroviral therapy can achieve a 1–2% or lower risk of mother-to-child transmission if maternal viral loads of 1,000 copies/mL or less can be sustained, independent of the route of delivery or duration of ruptured membranes before delivery. Vaginal delivery is appropriate for HIV-infected pregnant women who have been maintained on combined antiretroviral therapy and who have viral loads of 1,000 copies/mL or less at or near delivery. The risk of mother-to-child transmission in HIV-infected women with high viral loads can be reduced by performing cesarean deliveries before the onset of labor and before rupture of membranes (termed scheduled cesarean delivery in this document), in conjunction with the use of peripartum maternal antiretroviral therapy. Discussion of the option of scheduled cesarean delivery and its advantages in the situation of suboptimal viral suppression should begin as early as possible in pregnancy with every pregnant woman with HIV infection to give her an adequate opportunity to ask questions and consider her decision-making concerning the delivery plan. The patient's decision regarding her route of delivery should be respected after maternal and neonatal risks have been discussed.