Mother-to-child transmission (MTCT) of human immunodeficiency virus (HIV) is the main mode of acquisition in neonates, with approximately 20% of infants of untreated HIV-positive mothers becoming infected.¹ Acquisition risk is primarily dependent on maternal viral load and breastfeeding status; it is the highest during the last 2 trimesters of gestation, during labor and delivery, and while breastfeeding. Prior to 1994, there were no safety or efficacy studies examining the use of antiretroviral therapy (ART) to prevent MTCT.

To assess the safety and efficacy of zidovudine (AZT) for prevention of MTCT of HIV.

Double-blind, randomized placebo-controlled trial in 59 centers in the US and France from 1991 to 1993.