Pregnant women carry high HBV DNA loads before delivery, which is the most important factor leading to mother-to-child transmission of HBV. Nucleoside analogue antiviral treatment during late pregnancy can significantly reduce the incidence of HBV MTCT, but security problems of using NA treatment during pregnancy has not been eliminated, Therefore, the aim of our study is to explore the effect of starting to use Tenofovir Disoproxil Fumarate(TDF) antiviral treatment from the 32 weeks of gestation to block mother-to-child transmission of hepatitis B virus(HBV MTCT).