Parker SE, et al. - Using data from two large studies of birth defects, researchers delineated time trends in ondansetron use for the treatment of first-trimester nausea and vomiting of pregnancy. In addition, they examined the associations, either previously reported or undescribed, between first-trimester ondansetron use and major birth defects. They observed an increase in off-label use of ondansetron by 13% for the treatment of nausea and vomiting of pregnancy by the end of the study period. No increase in risk for the majority of specific birth defects investigated was noted in association with the first-trimester use of ondansetron for the treatment of nausea and vomiting of pregnancy compared with no treatment. However, further study is warranted in view of its modest associations with cleft palate and renal agenesis–dysgenesis.

Methods

• Using data from two case–control studies, the National Birth Defects Prevention Study (1997–2011) and the Slone Birth Defects Study (1997–2014), researchers calculated the prevalence of ondansetron use for the treatment of first-trimester nausea and vomiting of pregnancy among control patients in 2-year intervals.
• 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 were calculated using women with untreated first-trimester nausea and vomiting of pregnancy as the reference.
• They used a secondary exposure group of other prescription antiemetics to address confounding by indication.

Results

• Researchers analyzed 6,751 and 5,873 control mothers and 14,667 and 8,533 case mothers who reported first-trimester nausea and vomiting of pregnancy from the National Birth Defects Prevention Study and Slone Birth Defects Study, respectively.
• Increase in ondansetron exposure from less than 1% before 2000 to 13% in 2013–2014 was observed among women in the control group.
• They identified no association of ondansetron use with an increased risk for most of the 51 defect groups analyzed.
• They observed a modest increase in risk 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; however, these findings may be the result of chance.