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Issues Meriting Further Study in Preventing Mother-to-Infant Transmission of Hepatitis B by Antiviral Therapy During Pregnancy

Mother-to-infant transmission of hepatitis B virus (HBV) is a main cause of chronic HBV infection. Maternal high HBV DNA level or positive hepatitis B e antigen (HBeAg) is the major risk factor for the transmission. With recommended passive and active immunoprophylaxis, the transmission occurs in nearly 0 and 4–12% of infants born to HBV-infected mothers with negative and positive HBeAg, respectively. Therefore, pregnant women with negative HBeAg appear not requiring antiviral therapy to prevent mother-to-infant transmission of HBV. Recent studies demonstrated that oral antivirals (lamivudine, telbivudine, or tenofovir) in pregnant women with high viral load or positive HBeAg, starting from 28–32 weeks of gestation, together with neonatal immunoprophylaxis, can almost completely prevent the transmission, indicating that it does not require antiviral therapy before 28 weeks of gestation. Accumulated evidence showed that the antivirals may be stopped upon delivery, and the infants may receive breast feeding after birth. However, these issues, as well as HBV DNA threshold for antiviral therapy during pregnancy, optimal timing for start and discontinuation of antivirals, and the drug safety of fetuses/infants, require further investigations to optimize the antiviral therapy during pregnancy. The proof of safety of fetal exposure to antivirals needs more evidence, which can be achieved from the real-world data analysis. 
 
 
Key words: 
Antiviral therapy; Hepatitis B; Mother-to-infant transmission; Pregnant women