Human immunodeficiency virus (HIV) infections in children are usually acquired perinatally from their mothers. Dramatic declines in new childhood HIV infections since 1995 are attributable to the advent of combination antiretroviral therapies, and global efforts to prevent mother-to-child transmission. These efforts include HIV testing, providing antiretroviral treatment (ART) to pregnant and breastfeeding women living with HIV, antiretroviral (ARV) prophylaxis to infants born to mothers with HIV, intrapartum zidovudine when maternal viral load is not suppressed, and cesarean delivery. The recommendations for diagnosis, treatment, and prevention of HIV infection among pregnant women and their infants are constantly evolving, and the most current recommendations can always be found at https://clinicalinfo.hiv.gov .