Ovulation induction by clomiphene and neural tube defects

Several studies have investigated whether a woman's use of clomiphene citrate to stimulate ovulation was related to an increased risk for delivering off-spring with neural tube defects (NTDs). Findings from these reports have been inconsistent, with increased risks ranging from approximately none to nearly sixfold. Because the rarity of this exposure has precluded any single study from ascertaining sufficient numbers of exposed women to adequately assess risk, data from numerous studies will likely need to be considered together (e.g., meta-analysis) to facilitate a causal inference. In the spirit of providing additional information on this potential association, we present data from a recently completed large population-based case-control study of NTDs.