Study Finds No Risk of Birth Defects with Zofran During Pregnancy

Danish researchers indicate that the findings of new study failed to find any link between side effects of the anti-nausea drug Zofran and an increased risk of birth defects, contradicting prior results of a smaller study that suggested use of Zofran during pregnancy may increase the risk of cleft palate malformations. 

The new study was published this week in the New England Journal of Medicine, involving data on more than 600,000 pregnancies, which found no incidence of fetal harm among the 1,970 pregnancies that involved the use of Zofran.

Researchers looked at whether side effects of Zofran during pregnancy may increase the risk of various health problems, such as spontaneous abortion or birth defects, but no such correlation was found.

Zofran (ondansetron), which is manufactured by GlaxoSmithKline, is a member of a class of drugs known as 5-HT3 receptor antagonists, which work by blocking the actions of serotonin. It is commonly used for treatment of nausea caused by cancer treatments, but it has been widely used among pregnant women suffering from morning sickness, even though the FDA has not approved it for that use.

About 10% of pregnant women suffer from nausea severe enough that doctors recommend they take anti-nausea medication. However, a prior smaller study has raised concerns that Zofran could cross the placenta and adversely affect their child’s development or health. The previous study suggested that the drug could increase the risk of oral cleft birth defects, such as cleft palate and cleft lip, but those findings were not confirmed by this latest study.

Researchers found that significantly fewer women given Zofran suffered a spontaneous abortion, compared to women who did not take the drug, and there were no statistically significant differences in the rates of major birth defects, stillbirth, preterm delivery or delivery of a low-birth-weight infant, the findings indicate.

Known side effects of Zofran have been linked to a risk of a type of irregular heart rhythm, known as QT interval prolongation.  This may predispose patients to develop Torsades de Pointes, which may lead to sudden death if proper treatment is not received. In December 2012, the FDA announced a partial Zofran recall because of the heart rhythm problems associated with the drug. The recall only affects the 32 mg, single intravenous (IV) dose, which is usually used to prevent chemotherapy-induced nausea and vomiting.