Assessment of Potential Exposure to Pregnancy-Contraindicated Medications Among Women of Reproductive Age in Japan: A Retrospective Database Study.

Preconception care is globally recognized as essential for optimizing pregnancy outcomes; however, in Japan, comprehensive data on medication-related potential exposure to pregnancy-contraindicated medications among women of reproductive age remain limited. We conducted a retrospective cross-sectional descriptive study using data from Japan's National Database of Health Insurance Claims (fiscal year 2022) to assess the potential exposure to pregnancy-contraindicated medications among women of reproductive age. Outpatient prescriptions for oral medications dispensed to women aged 15-49 years were analyzed. In total, 270 medications classified as contraindicated during pregnancy were identified, of which 75 were also contraindicated for women planning pregnancy. Of these, 58 active ingredients were restricted in both phases. Notably, 212 medications were uniquely contraindicated during pregnancy, highlighting the broader contraindication profiles during fetal development than during the preconception period. Despite these contraindications, high prescription volumes were observed for medications such as loxoprofen sodium hydrate, sodium valproate, and metformin hydrochloride among women of reproductive age. These findings illustrate a high baseline utilization of pregnancy-contraindicated medications among women of reproductive age. As most women in this demographic are neither pregnant nor actively planning conception, these volumes primarily reflect standard care rather than inappropriate prescribing. In conclusion, pharmacists serve as an important supplementary safety net by routinely confirming pregnancy status to prevent inadvertent exposure.