Transplacental Transfer of Telbivudine in Hepatitis B Virus-Infected Pregnant Women Treated with Telbivudine during the Third Trimester

Telbivudine is an FDA-approved pregnancy category B drug for the treatment of chronic hepatitis B virus (HBV) infection. It has been used in HBV-carrier women with high viremia to prevent mother-to-child transmission of HBV. However, placental transfer of telbivudine from mother to fetus has not been studied. Using a sensitive ultraperformance liquid chromatography-tandem mass spectrometry method, we measured the concentration of telbivudine in maternal blood collected at delivery from 29 pregnant women, who took telbivudine (daily 600 mg) from gestation week 28-32 to week 4 postpartum, with a median interval of 8.0 (range 6.5-15.5) h between the final dose and sampling, and in cord blood collected from umbilical arteries of 29 placentas immediately after birth. The concentrations of telbivudine in maternal blood varied between 77.6 and 2920 ng/mL, with a median concentration of 379.0 ng/mL, while the concentrations in cord blood ranged from 107.0 to 2250 ng/mL, with a median concentration of 426.0 ng/mL. The concentration between the maternal and fetal circulations had no statistically significant difference (<i>P</i> = 0.6429). The median cord to maternal blood concentration ratio at delivery was 1.02 (IQR 0.70-1.25), and the mean ratio was 1.34, with a 95% CI of [0.88, 1.81]. Telbivudine may transplacentally transfer from the mother to fetus.