BACKGROUND Post-exposure prophylaxis administered to infants shortly after birth prevents approximately 90% of cases of perinatal hepatitis B virus (HBV) transmission. The Advisory Committee on Immunization Practices recommends that all pregnant women be tested for hepatitis B surface antigen (HBsAg) at an early prenatal visit during each pregnancy to detect active infection with HBV. This study sought to determine the proportion and characteristics of pregnant women tested\not tested according to Advisory Committee on Immunization Practices recommendations. METHODS We analyzed MarketScan databases to assess prenatal HBsAg testing among women with commercial and Medicaid health care coverage according to demographic and clinical characteristics. Pregnant women 15-44 years of age continuously enrolled in a health plan in the MarketScan database during 2013 and 2014 and with a live birth in 2014 were included. RESULTS Among commercially insured women, 239,955 (87.7%) received HBsAg testing and 59.6% were tested during their first trimester. Among Medicaid-enrolled women, 57,268 (83.6%) received HBsAg testing and 39.4% were tested during their first trimester. Among women with high risk pregnancies, HBsAg testing occurred in 87.3% of those with commercial insurance and 84.8% with Medicaid. Testing also varied by maternal age; among women with commercial insurance, testing was greatest among women 26-44 years of age, and among women with Medicaid, testing was greatest among younger women (15-25 years). Testing was lowest among women residing in the Northeast (commercial insurance only). CONCLUSIONS Prenatal HBsAg testing identifies HBV-infected pregnant women so their infants can receive timely immunoprophylaxis. Efforts to optimize HBsAg testing among all pregnant women are needed to further prevent perinatal HBV transmission.