Clomiphene citrate and neural tube defects: a meta‐analysis of controlled observational studies

Background At the end of the 1980s, several studies suggested a potential increased risk of neural tube defects (NTDs) with ovulation induction/fertility drugs, especially with clomiphene citrate (CC). A previous meta-analysis of observational studies evaluating the risk of NTDs associated with the use of CC performed in 1995 found a risk ratio of 1.08 (95% CI 0.76-1.51). Since then, additional studies have been published and the risk of NTDs associated with periconceptional CC exposure may have changed. Objective To perform an updated quantitative meta-analysis of the risk of NTDs associated with periconceptional CC exposure. Search strategy MEDLINE, Web of Science, and Scopus were searched (October 2018). Selection criteria Comparative cohort and case-control studies investigating the risk of NTDs after periconceptional CC exposure. Data collection and analysis Pooled effect sizes with corresponding 95% CIs were calculated using random effects models, comparing the risk of NTDs between pregnancies exposed and not exposed to CC. Main results Thirteen studies met the inclusion criteria, totalling 218 819 pregnancies. Periconceptional exposure to CC was not significantly associated with an increased risk of NTDs (pooled odds ratio 1.21, 95% CI 0.88-1.66). No heterogeneity between studies was observed (I-2 = 26%). A funnel plot and asymmetry test were not suggestive of publication bias. Conclusion Our meta-analysis confirms that exposure to CC before or in early pregnancy was associated with a 21% increased risk of NTD in relation to CC exposure; however, this increased risk is not statistically significant. Tweetable abstract A new meta-analysis finds that clomiphene citrate exposure before or in early pregnancy is not associated with an increased risk of NTDs.