Pregnancy outcomes following maternal exposure to ornidazole: a TERAFAR case series

To evaluate pregnancy outcomes after ornidazole exposure and describe major congenital malformations in a case series. Pregnant women who contacted the TERAFAR between 2010 and 2025 for ornidazole exposure in pregnancy with known outcomes were included. Maternal characteristics, exposure details, and outcomes were obtained from standardized records and postpartum interviews. The primary outcome was major congenital malformations; secondary outcomes were miscarriage, elective termination, stillbirth, preterm birth, and neonatal outcomes. Of 89 pregnancies analyzed, 71 (79.8%; 95% CI 69.9–87.6) resulted in live births, 14 (15.7%; 95% CI 8.9–25.0) in miscarriage, 3 (3.4%; 95% CI 0.7–9.5) in elective termination, and 1 (1.1%; 95% CI 0.0–6.1) in stillbirth. Among the 65 live-born infants with first-trimester ornidazole exposure, congenital malformations were identified in 5 (7.7%; 95% CI 2.5–17.0), including 4 major (6.2%; 95% CI 1.7–15.0) and 1 minor (1.5%; 95% CI 0.0–8.3) malformation. Major malformations were congenital heart defects ( n = 2), congenital glaucoma, and cleft lip. Ornidazole exposure during pregnancy was not associated with a strong teratogenic signal in this case series. The observed major malformation rate of 6.2%; however, the wide confidence interval included the approximate background prevalence of major congenital malformations. Although two of the four major malformations were congenital heart defects, the remaining malformations were phenotypically unrelated, and inconsistent exposure timing and case-specific confounding factors do not support associative attribution to ornidazole. These findings provide useful real-world data for counseling women inadvertently exposed to ornidazole, though the limited sample size and potential confounding warrant cautious interpretation. Larger controlled studies are needed to better define its safety profile in pregnancy.