Importance: Screening for hepatitis B virus (HBV) infection during pregnancy identifies women whose infants are at risk of perinatal transmission. Data from a nationally representative sample showed a prevalence of maternal HBV infection of 85.8 cases per 100000 deliveries from 1998 to 2011 (0.09% of live-born singleton deliveries in the United States). Although there are guidelines for universal infant HBV vaccination, rates of maternal HBV infection have increased annually by 5.5% since 1998. Children infected with HBV during infancy or childhood are more likely to develop chronic infection. Chronic HBV infection increases long-term morbidity and mortality by predisposing infected persons to cirrhosis of the liver and liver cancer. Objective: To update the 2009 US Preventive Services Task Force (USPSTF) recommendation on screening for HBV infection in pregnant women. Evidence Review: The USPSTF commissioned a reaffirmation evidence update to identify substantial new evidence sufficient enough to change the prior recommendation. The USPSTF targeted its evidence review on the effectiveness and potential harms of screening and the effectiveness and harms of case management to prevent perinatal transmission. Findings: The USPSTF previously found adequate evidence that serologic testing for hepatitis B surface antigen accurately identifies HBV infection. Interventions are effective for preventing perinatal transmission, based on foundational evidence and observational studies of US case management programs. In addition, there is evidence that over time, perinatal transmission has decreased among women and infants enrolled in case management, providing an overall substantial health benefit. Therefore, the USPSTF reaffirms its previous conclusion that there is convincing evidence that screening for HBV infection in pregnant women provides substantial benefit. Conclusions and Recommendation: The USPSTF recommends screening for HBV infection in pregnant women at their first prenatal visit. (A recommendation).