Abstract: Objective To investigate the efficacy and safety of tenofovir in the treatment of pregnant women with high serum HBV DNA loads. Methods The study had selected 83 pregnant women with high serum HBV DNA loads between March 2015 and September 2017，and 56 cases of them received tenofovir for antiviral therapy at the late gestation，and 27 didn’t. All the newborns received immediately hepatitis B immunoglobulin（HBIG） and hepatitis B vaccine after birth，and all the infants were followed-up for 12 months. The HBV infection was defined by serum HBsAg and/or HBV DNA positive. Results Serum HBV DNA load in women receiving tenofovir after delivery was（3.9±0.7） lg IU/ml，significantly lower than [（7.6±0.5） lg IU/ml，P<0.05]，serum HBsAg level was （674.3±301.9） IU/ml，significantly lower than [（1104.1±401.2） IU/ml，P<0.05]，and serum HBeAg level was（2059.8±996.4） s/co，significantly lower than [（3479.4±1287.6） s/co，P<0.05] in those without antiviral therapy；the successful block of mother-to-infant HBV infection in women with antiviral therapy was 100.0%，much higher than 81.5% （P<0.05） in those without；there was no adverse reaction caused by antiviral agent in tenofovir-treated women，and there was no significant difference in the growth and development indexes of newborns at birth between the two groups（P>0.05）. Conclusion The antiviral therapy with tenofovir administration for pregnant women with high serum HBV DNA loadS in late pregnancy has good effect on blocking intrauterine HBV infection with very good clinical safety.

Key words: Hepatitis B, Pregnancy, Tenofovir, Mother-to-child transmission, Block