National patterns of medication use during pregnancy.

Purpose: To describe patterns of medication use during pregnancy in ambulatory care settings according to the U.S. Food and Drug Administration (FDA) pregnancy risk classification.

Methods: A cross-sectional study of two national ambulatory care surveys, sampling all office visits made by pregnant women in 1999 and 2000, was conducted. Using the FDA pregnancy risk classification, patterns of medication use and predictive factors for FDA pregnancy risk D or X (D/X) medications were evaluated.

Results: In 1999 and 2000, about half of all pregnant visits had one or more medications. Among the total visits, FDA Class A was the majority (private = 65.7%; hospital = 79.5%; p < 0.05) followed by Class C (private = 26.5%; hospital = 36.4%; p < 0.05). Class D/X medications accounted for 6.4% and 2.9% of visits in private and hospital, respectively (p < 0.05). Medications with unknown pregnancy categories were predominant in the private setting (12.0% and 3.9%; p < 0.05). Age, insurance type, region, physician specialty, and number of medications were associated with a category D/X prescription. Among hospital visits, those from the West region and with private insurance were more likely to receive category D/X prescriptions. Number of medications was strongly associated with high-risk drugs in both settings.

Conclusions: This study shows considerable medication use among pregnant women. The prevalence of visits with FDA pregnancy category D/X drugs was moderate, but still indicates exposure to high-risk medications.