Abstract: Objective To evaluate the efficacy and safety of telbivudine in blocking intrauterine HBV transmission. Methods 28 pregnant women with chronic hepatitis B were treated by telbivudine（600mg/d）since 28 weeks of gestation to 4 weeks after delivery，and 30 pregnant women with HBV infection were without antiviral teatment.The newborn were given active/passive immunization. Results The HBV DNA levels in treatment group before delivery were significantly declined[7.5±0.6 lg copies/ml to 3.3±1.6lg copies/ml（t=9.59，P<0.001）]，while the serum HBV DNA levels in control group didn't change；the incidence of intrauterine HBV infection in control was 13.3%（4/30，x2=4.15，P<0.05），much higher than that in the treatment group（0%）；the untoward effect of telbivudine was mild and not different between the two group. Conclusion Telbivudine can reduce the incidence of intrauterine HBV infection in the late pregnant women with chronic hepatitis B viral infection.

Key words: Hepatitis B, Vertical transmission, Intrauterine infection, Telbivudine