 In the present study, we evaluated the effect of telbivudine given during the second and third trimesters of pregnancy to highly viremic, HBV DNA-positive mothers on maternal HBV DNA and HBeAg levels prior to delivery and the rate of vertical transmission of HBV to infants who received passive-active immunoprophylaxis. Additionally, we investigated the timing of the administration of telbivudine on reducing the risk of perinatal transmission and the safety of telbivudine during pregnancy. 