In a cohort of HBeAg-positive mothers with an HBV DNA level of more than 200,000 IU per milliliter during the third trimester, the rate of mother-to-child transmission was lower among those who received TDF therapy than among those who received usual care without antiviral therapy. (Funded by Gilead Sciences; ClinicalTrials.gov number, NCT01488526.).

(Abstracted from N Engl J Med 2016;374:2324–2334) Hepatitis B virus (HBV), a leading cause of cirrhosis and liver cancer, is a serious health threat, and prevention of HBV transmission is an important part of the strategy to alleviate infection and its outcomes. Hepatitis B virus can be vertically transmitted from mothers to fetuses during childbirth, and infants who are untreated can consequently develop chronic infection.