The safety of 3TC (lamivudine, Epivir) in human pregnancy has not been definitively established. However, while animal studies have failed to show evidence of foetal malformations, studies in rabbits have shown that 3TC can cause death of the embryo in early pregnancy. Based on these studies, 3TC administration is not usually recommended for the first three months of pregnancy.

There is evidence that 3TC plus AZT (zidovudine, Retrovir) can significantly reduce mother-to-child transmission of HIV. A French study of 445 HIV-infected pregnant women found that the transmission rate was reduced to 2% when mothers took AZT and 3TC from week 32 of pregnancy until delivery and the combination was administered to the babies for the first six weeks of life[1]. However, the use of only two drugs by pregnant women may induce drug resistance and may undermine the benefits of subsequent antiretroviral treatment.