An increasing number of antiretroviral agents (ARVs) are approved for use, but their use during pregnancy in the United States has not been completely described. We used data from the Pediatric HIV/AIDS Cohort Study (PHACS) Surveillance Monitoring for ART Toxicities (SMARTT) study, a United States-based prospective cohort study of HIV-exposed but uninfected children, to assess temporal trends and maternal characteristics associated with the use of ARVs during pregnancy. The proportion of children exposed in utero to ARVs was calculated over time. A multivariable logistic regression model was used to estimate associations of maternal characteristics with use of highly active antiretroviral therapy (HAART) during pregnancy. We studied 1768 HIV-exposed but uninfected children born between 1995 and 2009 and enrolled in SMARTT. Prenatal HAART exposure increased from 19% in 1997 to 88% in 2009. Of children born in 2009, 99% had prenatal exposure to NRTIs (including zidovudine, 73%; lamivudine, 72%; tenofovir, 39%; and emtricitabine, 37%). Exposure to protease inhibitors increased from 15% in 1997 to 86% in 2009, while exposure to non-nucleoside reverse transcriptase inhibitors (NNRTIs) declined from 33% in 2003 to 11% in 2009. Higher maternal HIV RNA viral load (VL) concentration, lower maternal CD4 count, and earlier timing of the first maternal CD4 or VL measurement during pregnancy were associated with increased odds of HAART exposure. Prenatal HAART exposure has increased but is not universal. As ARV use during pregnancy continues to evolve, follow-up of children is needed to assess long-term effects of ARV exposures.