Comparison of TAF and TDF in Preventing Mother-to-Child Transmission of HBV in Pregnancies With High Viral Loads

Inclusion Criteria: 1. Pregnant women aged between 20 and 40 years old 2. Pregnancy duration between 20 to 28 weeks (screening for eligible patients can start from the 20th week of gestation) 3. Clinically diagnosed with compensated chronic hepatitis B, HBsAg positive for more than 6 months, with clinical history, signs, and test results consistent with compensated chronic hepatitis B 4. HBsAg and HBeAg positive in maternal serum during screening 5. PCR testing shows maternal serum HBV DNA levels exceeding 200,000 IU/mL 6. Subjects voluntarily agree to undergo treatment according to the study design's drug treatment plan and all other research requirements, and patients consent to strictly avoid pregnancy within 28 weeks postpartum 7. Patients and their husbands (the biological parents of the child) understand the risks and voluntarily participate in the study. The mother must participate voluntarily and sign a written informed consent document before participating in the study. Exclusion Criteria: 1. Creatinine clearance \< 100 mL/min (calculated using the Cockcroft-Gault method based on serum creatinine and ideal body weight), or hypophosphatemia (below normal range). 2. History of adverse renal reactions induced by Adefovir or history of Adefovir resistance. 3. Meeting one of the following criteria: hemoglobin \< 80 g/L, neutrophil count \< 1000/μL, ALT \> 5 times the upper limit of normal, total bilirubin \> 20 mg/L, albumin \< 25 g/L, abnormal levels of creatinine or urea nitrogen. 4. Pregnant women with a history of miscarriage, history of giving birth to a child with congenital malformations, or history of fetal infection with hepatitis B virus. 5. The biological father of the current pregnancy has chronic hepatitis B. 6. The investigator assesses that the subject has significant kidney, cardiovascular, pulmonary, or neurological diseases that affect their participation in the study.