Preventing Mother-to-child Transmission of Hepatitis B Virus With Tenofovir Alafenamide (TAF)

Inclusion Criteria: * Pregnant woman aged 20 to 35 years old * 24-26 week of gestation * HBsAg positive more than 6 months and HBeAg positive * HBV DNA\> 200,000 IU/ml * Informed consent is signed voluntarily by both husband and wife * Good compliance and able to be followed up as planned Exclusion Criteria: * Mothers co-infected with HCV and HIV * Evidence of decompensated cirrhosis and liver cancer * Mothers had other organ lesions which would affect patient compliance and follow-up plan * Mothers had history of spontaneous abortion or their children had birth defect or congenital malformation * Mothers received antiviral therapy within 6 months * Mothers had history of kidney injury, CCr \<50ml/min and urine protein test positive (\>300mg/L) * Mothers had history of other chronic diseases and had to take immunomodulators, cytotoxic drugs or hormonal drugs during pregnancy * The infants' biological fathers are infected with HBV * Symptoms of threatened abortion during early pregnancy * ALT \> 1×upper limit of normal (ULN), or TBIL ≥ 1×ULN or glomerular filtration rate (GFR) \< 90 ml/min, or Albumin (ALB) \< 25 g/L * Fetal malformations detected by B-ultrasound during pregnancy * Participating in other studies