To evaluate the prevalence, trends, timing and duration of exposure to antiviral medications during pregnancy within a US cohort of pregnant women and to evaluate the proportion of deliveries with a viral infection diagnosis among women given antiviral medication during pregnancy. Live-born deliveries between 2001 and 2007, to women aged 15-45 years, were included from the Medication Exposure in Pregnancy Risk Evaluation Program, a collaborative research program between the U.S. Food and Drug Administration and eleven health plans. They were evaluated for prevalence, timing, duration, and temporal trends of exposure to antiviral medications during pregnancy. We also calculated the proportion of deliveries with a viral infection diagnosis among those exposed to antiviral medications. Among 664,297 live births, the overall prevalence of antiviral exposure during pregnancy was 4 % (n = 25,155). Between 2001 and 2007, antiviral medication exposure during pregnancy doubled from 2.5 to 5 %. The most commonly used antiviral medication was acyclovir, with 3 % of the deliveries being exposed and most of the exposure occurring after the 1st trimester. Most deliveries exposed to antiviral medications were exposed for less than 30 days (2 % of all live births). Forty percent of the women delivering an infant exposed to antiviral medications had a herpes diagnosis. Our findings highlight the increased prevalence of women delivering an infant exposed to antiviral medications over time. These findings support the need for large, well-designed studies to assess the safety and effectiveness of these medications during pregnancy.