Ovulation induction and risk of neural tube defects.

The relation between use of ovulation-inducing drugs and risk of neural tube defects (NTDs) was studied in a case-control surveillance programme. The frequency of any use of such drugs during the 6 months before the last menstrual period or during pregnancy was 3.0% for 1034 mothers of infants and fetuses with NTDs (cases) and 2.8% for 4081 mothers of those with other major congenital malformations (controls) (relative risk 1.1, 95% CI 0.8-1.7). Relative risks for clomiphene and for hormones were 0.8 (0.5-1.3) and 1.5 (0.7-3.4), respectively. These data suggest that use of ovulation-inducing drugs before conception does not increase the risk of NTDs.