Pregnancy outcome following in-utero exposure to ondansetron: A prospective comparative observational study

The objective of the study was to evaluate the rate of major congenital anomalies after first trimester exposure to ondansetron for nausea and vomiting of pregnancy (NVP). The design is a prospective, comparative, observational cohort study, performed at the Israeli Teratology Information Service between 2010 and 2014. Follow-up was obtained for 195 ondansetron-exposed, 110 metoclopramide-exposed, and 778 pregnancies with non-teratogenic exposure (NTE). The overall rate of major anomalies did not significantly differ between the groups [4/200 = 2.0 % (ondansetron), 1/109 = 0.9 % (metoclopramide), and 13/731 = 1.8 % (NTE)]. All the anomalies in both the ondansetron and metoclopramide groups, and 6/13 anomalies in the NTE group, were cardiac septal defects most of which spontaneously resolved. Both ondansetron (adjHR = 0.29, 95 % CI 0.10-0.80) and metoclopramide (adjHR = 0.27, 95 % CI 0.08-0.86) were associated with lower miscarriage rate compared to NTE. Based on the present study, ondansetron during pregnancy is not associated with an increased risk for overall major anomalies, nor for clinically important cardiac defects. It may be a reasonable alternative for women with severe NVP who do not respond to first line medications.