Principal objective: Assess the effectiveness of a strategy to prevent HBV mother-to-child transmission (MTCT) in Cambodia based on the use of rapid tests HBs Ag and HBe Ag to screen HBV infection and a treatment by TDF for patients with a positive HBeAg test with a "test and treat" strategy for those seen for Antenatal Care (ANC) from 24 weeks of amenorrhea.