In the United States, approximately 5,000 women living with HIV infection give birth each year. HIV can be transmitted from a mother to her child at any time during pregnancy, labor and delivery, and breastfeeding. Because of effective preventive measures, the transmission rate from pregnant women to their children has declined significantly. Strategies to prevent mother-to-child transmission include maternal and infant antiretroviral therapy and formula-feeding instead of breastfeeding. All infants born to mothers with HIV infection should receive antiretroviral postexposure prophylaxis as soon as possible, ideally within six hours after delivery. The type of prophylaxis depends on whether the mother has achieved virologic suppression, defined by an HIV RNA load of less than 50 copies per mL, and if the infant is at high risk of vertical transmission of HIV. Risk factors for vertical transmission include maternal seroconversion during pregnancy or breastfeeding, high maternal plasma viral RNA load during pregnancy, and advanced maternal HIV disease.