Purpose: Perinatal exposure, either in utero or more often during delivery, is an important mode of hepatitis B virus (HBV) transmission that results in chronic disease in approximately 90% of infected infants. Immunoprophylaxis (consisting of hepatitis B vaccine and hepatitis B immune globulin [HBIG]) is recommended for infants born to hepatitis B-infected women within 12 hours of birth and is 95% effective in preventing perinatal HBV transmission. For women with high viral loads (>200,000 IU/mL), antiviral therapy during pregnancy has been recently recommended to further reduce perinatal transmission risk. We sought to characterize antiviral therapy use in hepatitis B-infected pregnant women. Methods: The Centers for Disease Control and Prevention (CDC) funds 64 state and local jurisdictions to collect information on pregnant women infected with hepatitis B and their infants as part of its Perinatal Hepatitis B Prevention Program. CDC provided auxiliary funding for five jurisdictions to collect additional information on maternal and infant demographic and clinical characteristics. We analyzed data collected retrospectively from hepatitis B-infected pregnant women in Georgia, Michigan, New York City, Philadelphia, and Wisconsin identified as having delivered live births during April 2016-December 2017. We assessed maternal antiviral therapy use during pregnancy; HBV DNA levels included in our analysis were from the last result available prior to delivery for each woman. Results: We identified 3,971 women with hepatitis B infection during pregnancy; of these, 803 (20.2%) had information regarding prescription of antiviral therapy during pregnancy. HBV DNA levels were known for 1907 women, of whom 9.1% (n=173) had HBV DNA >200,000 IU/mL nearest delivery. Antiviral therapy was prescribed for 26.5% (n=213) of women with information. Antiviral therapy was more commonly prescribed for women aged <30 years vs. ≥30 years (32.0% vs. 23.1%, p=0.0069), Asian/Pacific Island race vs. white or black (42.7% vs. 2.8% and 6.2%, respectively, p<0.0001), and those whose HBV was monitored by a gastroenterologist/hepatologist vs. maternal fetal medicine or infectious disease specialist (55.1% vs. 10.3% and 36.4%, respectively, p<0.0001). Tenofovir was prescribed for 92.9% of women prescribed antiviral therapy; lamivudine was prescribed for 3.8%. Mean birth weight was 3196.7 grams and 3224.7 grams for infants born to mothers prescribed and not prescribed antiviral therapy, respectively (p=0.4713). Conclusion: Antiviral therapy was prescribed for approximately one-fourth of hepatitis B-infected pregnant women with information. Antiviral therapy was prescribed more commonly for women who were younger, Asian/Pacific Island race, and who received hepatitis B care from a gastroenterologist/hepatologist. Although these are preliminary findings and data collection is ongoing, opportunities may exist to improve guideline-concordant antiviral therapy use among pregnant women.