The goal of this clinical trial is to learn the efficacy and safety of Tenofovir alafenamide (TAF) vs Tenofovir disoproxil fumarate(TDF) in early and middle pregnancy antiviral therapy for chronic hepatitis B pregnant women.

The main questions it aims to answer are:

The rate of HBV mother-to-child transmission between the TAF and TDF groups. The incidence of birth defects in newborns between the TAF and TDF groups. What medical problems do participants have when taking drug TAF or TDF? The growth and development indices of newborns between the TAF and TDF groups.

Participants will:

Take drug TAF or TDF every day during the pregnacy. Visit the clinic once every 4 weeks for checkups and tests during the pregnancy and every 12 weeks postpartum.

Inclusion Criteria:

Female gender. Age between 20-40 years old. Positive for HBsAg for ≥6 months. Pregnant at 0-24 weeks meeting the 2022 China Chronic Hepatitis B guidelines for antiviral therapy (including but not elevated transaminases, liver cirrhosis, hepatic fibrosis, or extrahepatic manifestations of hepatitis B).

Willingness to take TAF/TDF orally once daily from enrollment until delivery or long-term use.

Good medication compliance.

Exclusion Criteria:

Co-infection with hepatitis A, C, E viruses, other hepatotropic viruses, or HIV.

Liver cirrhosis, liver cancer, or other chronic liver diseases. Significant organ diseases (e.g., heart, lung, or kidney diseases). Autoimmune hepatitis, autoimmune diseases, hypertension, diabetes, or thyroid disorders.

History of pregnancy complications. History of fetal/neonatal growth defects in previous pregnancies. Use of nephrotoxic drugs, corticosteroids, NSAIDs, cytotoxic drugs, or immunomodulators prior to enrollment.

Abnormal ultrasound findings indicating fetal malformations, placental abnormalities, or threatened miscarriage before treatment initiation.

Failure to attend follow-up visits as scheduled.

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