Tenofovir in Late Pregnancy to Prevent Vertical Transmission of Hepatitis B Virus

Immunoprophylaxis failure of hepatitis B virus (HBV) leading to vertical transmission remains a concern and has been reported in approximately 8-15% of infants born to hepatitis B e antigen (HBeAg) positive mothers with high levels of HBV DNA. Maternal HBV DNA \> 6log10 copies/mL (or \>200,000 IU/mL) is the major risk for the mother-to-child transmission. Prior observational studies have shown that antiviral therapy including lamivudine or telbivudine use during late pregnancy can safely reduce the rate of vertical transmission in this special population compared to untreated patients. Tenofovir Disoproxil (TDF), a pregnancy category B medication, reduces HBV DNA and normalizes serum alanine aminotransferase (ALT) in chronic hepatitis B patients (CHB) with few adverse effects. Two aspects on tenofovir use in pregnancy will be evaluated prospectively in this study: 1. The data on its tolerability and safety in HBeAg+ pregnant women with HBV DNA \> 6log10 copies/mL (or \> 200,000 IU/mL) during late pregnancy and infants. 2. Its efficacy in the reduction of HBV vertical transmission rate.