Ondansetron for Treatment of Nausea and Vomiting of Pregnancy and the Risk of Specific Birth Defects.

OBJECTIVE

To use data from two large studies of birth defects to describe time trends in ondansetron use for the treatment of first-trimester nausea and vomiting of pregnancy and to investigate associations, either previously reported or undescribed, between first-trimester ondansetron use and major birth defects.

METHODS

We used data from two case-control studies, the National Birth Defects Prevention Study (1997-2011) and the Slone Birth Defects Study (1997-2014). The prevalence of ondansetron use for the treatment of first-trimester nausea and vomiting of pregnancy among control patients was calculated in 2-year intervals. Using women with untreated first-trimester nausea and vomiting of pregnancy as the reference, we calculated adjusted odds ratios (ORs) and 95% CIs for associations between first-trimester ondansetron use for treatment of nausea and vomiting of pregnancy and specific birth defects. A secondary exposure group of other prescription antiemetics was used to address confounding by indication.

RESULTS

In the National Birth Defects Prevention Study and Slone Birth Defects Study, respectively, 6,751 and 5,873 control mothers and 14,667 and 8,533 case mothers who reported first-trimester nausea and vomiting of pregnancy were included in the analysis. Among women in the control group, ondansetron exposure increased from less than 1% before 2000 to 13% in 2013-2014. Ondansetron use was not associated with an increased risk for most of the 51 defect groups analyzed. Modest increases in risk were observed for cleft palate (adjusted OR 1.6, 95% CI 1.1-2.3) in the National Birth Defects Prevention Study and renal agenesis-dysgenesis (adjusted OR 1.8, 95% CI 1.1-3.0) in the Birth Defects Study, although these findings may be the result of chance.

CONCLUSION

Off-label use of ondansetron for the treatment of nausea and vomiting of pregnancy increased to 13% by the end of the study period. For the majority of specific birth defects investigated, there was no increased risk associated with first-trimester use of ondansetron for treatment of nausea and vomiting of pregnancy compared with no treatment, although modest associations with cleft palate and renal agenesis-dysgenesis warrant further study.