Objective: The purpose of this study was to investigate placental transfer and amniotic fluid concentrations of lamivudine in human immunodeficiency virus-infected women who received the agent during pregnancy.
Study design: Mothers in the study were receiving antiretroviral therapy that included lamivudine in a clinical setting. Maternal blood, cord blood, and amniotic fluid samples were obtained simultaneously at the time of delivery from 57 mother-infant pairs.
Results: At a median of 8.5 hours after the last maternal oral 150-mg dose of lamivudine, median maternal and fetal plasma concentrations were 302 and 240 ng/mL, respectively. Individual maternal and fetal concentrations were strongly correlated (r2 = 0.36; P < 10(-4)), and their median ratio was about 1. The median concentration in the amniotic fluid was 5 times higher than that in maternal plasma (upper range of ratio, 133).
Conclusion: Lamivudine appeared to cross the placenta by simple diffusion and is concentrated in the amniotic fluid. High amniotic fluid levels of lamivudine may carry both benefits and risks for the child.