Post-Conceptional Exposure to Clomiphene Citrate and Congenital Malformations: A Cohort Study

Background Clomiphene citrate is an ovulation inductor for which inadvertent post-conceptional exposures may occur in early pregnancy. In preclinical studies, post-conceptional exposures showed a teratogenic effect in different species. In humans, to date, little is known about the outcomes of inadvertently post-conceptionally exposed pregnancies. Objectives The objectives of our study were to assess the association between post-conceptional exposures to clomiphene citrate and major and minor congenital malformations in the offspring. Methods A retrospective cohort study of prospectively ascertained cases was undertaken, based on clinical data from the Centre de Référence sur les Agents Tératogènes (CRAT), Paris, France. Women with post-conceptional exposure to clomiphene citrate (n = 309), and unexposed pregnant women (n = 1236, 1:4 ratio) with prospectively collected data, known pregnancy outcome and delivery date prior to 01/02/2022, were matched by calendar year. An adjudication committee classified major and minor congenital malformations according to the EUROCAT (European Registration of Congenital Anomalies and Twins) classification. Results Among post-conceptional exposed women, no increased risk of major malformation was found (crude relative risk = 0.64, 95% confidence interval 0.19–2.15) as compared to unexposed women. Three major and ten minor congenital malformations were reported in the exposed group. An increased risk of minor malformations was found (crude relative risk = 4.05, 95% confidence interval 1.70–9.64) although there was no specific clinical pattern. Conclusions Post-conceptional exposure to clomiphene citrate was not associated with an increased risk of major congenital malformations. Given potential confounding and information biases, the results about minor malformations should be interpreted with caution as no specific clinical pattern was identified.