This means that around 1 million pregnant American women are exposed to ondansetron out of 4 million pregnancies a year. Ondansetron (GlaxoSmithKlein Inc, Philadelphia, PA) is a serotonin 5-HT3 receptor antagonist, originally introduced to prevent nausea and vomiting induced by cancer chemotherapy, radiation therapy, and surgery. The fact that ondansetron became generic in 2007, and hence its price dropped, might have been an important cause for this increase, with easier access to Medicaid and health maintenance organizations. Prescribing ondansetron as a first line option is not consistent with American Professors in Gynecology and Obstetrics and American College of Obstetricians and Gynecologists evidence-based recommendations for the management of NVP