Surprisingly, and for all the widespread off-label use of Zofran (ondansetron) for morning sickness in pregnancy, there has been only one study of its linkage to birth defects in the United States. And that research, jointly conducted by the Slone Epidemiology Center in Boston and the Centers for Disease Control and Prevention in Atlanta, detected a more than two-fold increase risk of cleft-palate associated with Zofran taken for nausea and vomiting in the first trimester of pregnancy.
In late 2013, Australian researchers reported on a small group of 251 women who took Zofran (ondansetron) during their pregnancy. Notably, there was a 20% increased risk of a major birth defect among the children exposed to Zofran during the first trimester. This outcome was very similar to the increased risk of major birth defects found in a Danish study reported earlier that year.
Another notable finding from the Australian study was that preterm births were more common among the infants exposed to Zofran, as were a number of other adverse pregnancy outcomes. Among these were low APGAR scores, lower birth weights, and shorter infant length.
A vast majority of the recent Zofran (ondansetron) studies around the world have concluded that this drug significantly increases the risk of birth defects in children whose mothers were prescribed this drug during the first trimester of pregnancy. The 2013 Australian study further serves to emphasize this point.
In concluding their paper, the Australian authors strongly urged that “it is important to accumulate a large cohort of patient outcomes to address [Zofran’s] safe use in pregnancy, including investigating the risk for specific birth defects.”