Motherisk update. Is ondansetron safe for use during pregnancy?

While I usually prescribe doxylamine-pyridoxine for morning sickness, some of my patients with severe nausea and vomiting of pregnancy (NVP) receive ondansetron in hospital. I have read some new precautions recommended by the US Food and Drug Administration (FDA). Is ondansetron safe to use during pregnancy?

During the past decade ondansetron has been increasingly used in the United States for NVP, owing to the lack of an FDA-approved drug for this condition. While fetal safety data for doxylamine-pyridoxine are based on more than a quarter of a million pregnancies, the fetal safety data for ondansetron are based on fewer than 200 births. Moreover, a recent case-control study suggested there was an increased risk of cleft palate associated with ondansetron. Recently, the FDA issued a warning about potentially serious QT prolongation and torsade de pointes associated with ondansetron use; the warning included a list of precautions and tests that must be followed. The drug is not labeled for use in NVP in either the United States or Canada. Based on the data available today, ondansetron use cannot be assumed to be safe during pregnancy.