Reducing Vertical Transmission of Hepatitis B in Africa

Inclusion Criteria: * prenatal clinic patient, * age ≥16 years, * 14-32 weeks gestational age according to clinic dating based on LMP or ultrasound, * active hepatitis B with risk of vertical transmission (HBsAg+ AND HBeAg+ or HBV DNA \>1000 IU/ML), * plan to receive follow up care and deliver at study facility, * capable of providing informed consent. Exclusion Criteria: * HIV positive (according to HIV antibody testing performed at the initial prenatal visit) * known liver cirrhosis or end-stage liver disease, * elevated liver enzymes (ALT \>5x upper limit of normal), * elevated serum creatinine (\>1.4 mg/dl) * currently taking tenofovir medication * allergy or intolerance to tenofovir study medication, * known fetal anomaly in the current pregnancy, * clinical illness requiring hospitalization at the time of enrollment * evidence of early labor at the time of enrollment.