Research News

Ondansetron looks safe in pregnancy, so far

BMJ 2013; 346 doi: (Published 06 March 2013) Cite this as: BMJ 2013;346:f1387


The popular antiemetic ondansetron looked safe for pregnant women in a large study from Denmark. The authors found no evidence of harm to the unborn baby in a series of analyses of more than 600 000 singleton pregnancies tracked through five of Denmark’s national registries.

Women prescribed ondansetron were no more likely to have babies with major birth defects than those not prescribed the drug (2.9% v 2.9%; prevalence odds ratio 1.12, 95% CI 0.69 to 1.82). They were no more likely to have a spontaneous abortion, a preterm birth, a stillbirth, or a baby that was small for gestational age. Women prescribed ondansetron in the first trimester had significantly fewer spontaneous abortions (1.1% v 3.7%; hazard ratio 0.49, 0.27 to 0.91). This is probably because nausea and vomiting in early pregnancy are associated with lower risk, say the authors.

The authors used a propensity score to match cohorts of exposed and unexposed women. They controlled confounding by indication using hospital admissions for nausea and vomiting. The study is considerably bigger than previous ones on the safety of ondansetron in pregnancy and the results are reassuring, they write.

Almost 2000 women in the cohort were prescribed ondansetron (1970; 0.3%), often in the first trimester, and almost always before 22 weeks’ gestation (1849/1970).


Cite this as: BMJ 2013;346:f1387