The major mode of acquisition of human immunodeficiency virus (HIV) for children is through mother-to-child transmission, which can occur during pregnancy or labor and delivery, or postnatally through breastfeeding. In resource-rich countries, mother-to-child HIV transmission has decreased to less than 2 percent after recommendations for universal prenatal HIV counseling and testing, antiretroviral prophylaxis and elective cesarean delivery, and avoidance of breastfeeding were implemented. In resource-limited settings, effective, shorter, and less expensive antiretroviral prophylaxis interventions also have been identified, but implementation has been slower, and continued transmission through breastfeeding remains a significant problem. This review summarizes recent advances made in prevention of mother-to-child transmission of HIV in the United States and other resource-rich countries, as well as progress in resource-limited countries.