Zofran (ondansetron), manufactured by GlaxoSmithKline (GSK), is a member of a class of drugs known as 5-HT3 receptor antagonists, which work by blocking the actions of serotonin. Zofran is commonly prescribed for use by pregnant women suffering from morning sickness. Studies show that Zofran use by pregnant women can lead to a heightened risk of severe birth defects, including heart development irregularities, cleft lip and cleft palate.

A recent study by researchers at Harvard and Boston University’s Slone Epidemiology Center show that women exposed to Zofran, or a generic form of ondansetron, were 2.37 times more likely to deliver a baby with a cleft palate. These findings follow a series of epidemiological studies that have found an increased risk of major birth defects associated with exposure to Zofran during early pregnancy. For example, Swedish researchers, analyzing birth records from 1998 through 2012, concluded that “mothers who took Zofran during early pregnancy had a 62% increased risk of having a baby with a cardiovascular defect.”