Background: HIV-1 infection may impair transplacental antibody transfer to infants. The impact of highly active antiretroviral treatment (ART) given during pregnancy on transplacental antibody transport is unknown. Methods: HIV-1 infected pregnant women with CD4 counts between 200-500 were randomized to short-course zidovudine (ZDV) or triple ART at 32 weeks gestation for prevention of mother-To-child HIV-1 transmission. Levels of maternal antibody against measles, pneumococcus and rotavirus at delivery, and antibody transfer to the baby through cord blood, were compared between trial arms. Results: Overall, 141 and 148 women were randomized to triple ART and ZDV, respectively; cord blood was for a subset (n = 20 in triple ART and n = 22 in ZDV). Maternal antibody levels to all pathogens during pregnancy and at delivery were not significantly different between arms. Within each arm, antibody levels at delivery were lower than at enrolment. For all antibodies, a woman's levels before delivery were an important predictor of amount transferred to her infant. Women on triple ART transferred higher levels of pathogen-specific antibodies when compared with women on short course ZDV. Conclusions: Women on triple ART transferred higher levels of pathogen-specific antibodies compared with women on ZDV alone.