Case Series Finds No Strong Teratogenic Signal for Ornidazole in Pregnancy

The study, published in Archives of Gynecology and Obstetrics, draws on records from TERAFAR, a teratology information service that pregnant women contacted with questions about medication safety in pregnancy. The researchers identified pregnant women who contacted the service between 2010 and 2025 regarding ornidazole exposure in pregnancy and whose pregnancy outcomes were known. Maternal characteristics, exposure details and outcomes were obtained from standardized records and postpartum interviews.

The primary outcome the team tracked was major congenital malformations, with miscarriage, elective termination, stillbirth, preterm birth and neonatal outcomes recorded as secondary outcomes.

In total, 89 pregnancies were analyzed. Of these, 71, or 79.8 percent, resulted in live births, with a 95 percent confidence interval of 69.9 to 87.6 percent. Fourteen pregnancies, 15.7 percent, ended in miscarriage, three, 3.4 percent, in elective termination, and one, 1.1 percent, in stillbirth. These figures describe the outcomes observed in this particular cohort of callers and are not directly comparable to unexposed population rates without the caution that the confidence intervals are wide.

Four of the five were classified as major malformations, giving a major malformation rate of 6.2 percent, and one was classified as minor.

The four major malformations included two congenital heart defects, one case of congenital glaucoma and one cleft lip. This pattern of defects is notable precisely because it is phenotypically scattered. Here, the researchers observed no such coherent signature, and the exposure timing varied across cases, which the authors state does not support associative attribution to ornidazole.

The authors also weighed the headline malformation rate against its statistical uncertainty. In other words, the observed rate in this small series is statistically compatible with what would be expected in any unselected group of pregnancies, even if no drug exposure had occurred at all.

Case series of this kind carry inherent limitations that the authors acknowledge directly. The authors emphasize that these findings warrant cautious interpretation and that larger controlled studies are needed to better define ornidazole’s safety profile in pregnancy.

Even with those caveats, the study fills a genuine gap. For clinicians counseling a woman who took ornidazole before realizing she was pregnant, the practical takeaway from this work is that the observed outcomes do not suggest a strong teratogenic risk, while the uncertainty around the point estimates means the data should be presented as limited rather than definitive.

The research team, led by Mesut Gungor and Yusuf Cem Kaplan with colleagues, notes that the findings provide useful real-world data for counseling women with inadvertent exposure. As the article is published under open access as an accepted, peer-reviewed manuscript ahead of the final version of record, the figures reported here may be subject to minor editorial revision in the final published version.

Subject of Research: Pregnancy outcomes after maternal ornidazole exposure, studied through a teratology information service case series

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

Article References: Gungor, M., Horoz, E., Kuragi, C. C., Bakirli, D. C., Eskiyurt, B., Karakulak, O., Karadas, B., Yilmaz, I., & Kaplan, Y. C. (2026). Pregnancy outcomes following maternal exposure to ornidazole: a TERAFAR case series. Archives of Gynecology and Obstetrics. https://doi.org/10.1007/s00404-026-08542-9

Image Credits: AI Generated

DOI: 10.1007/s00404-026-08542-9

Keywords: ornidazole, pregnancy, teratogenicity, congenital malformations, TERAFAR, teratology information service, first trimester exposure, drug safety, miscarriage, case series, nitroimidazole, Archives of Gynecology and Obstetrics