The use of ondansetron, an anti-nausea medication originally developed for cancer treatment, has increased significantly among pregnant women experiencing morning sickness in New Zealand, according to recent research by a University of Otago public health expert. Dr. Sarah Donald’s study found that ondansetron prescriptions during pregnancy rose from nearly negligible levels in 2005 to 9.1% by 2019.
Despite its growing use, ondansetron has not been formally approved to treat nausea and vomiting in pregnancy, making its use in this context “off label.” Clinical guidelines during much of the study period recommended ondansetron only after other anti-nausea medications had failed. However, Dr. Donald noted that over time, the drug has increasingly been prescribed as a first-line treatment. Factors contributing to its popularity include a relaxation of prescribing restrictions and the availability of ondansetron in a convenient dissolvable tablet form. More recent guidelines now endorse ondansetron as one option for initial treatment, particularly in cases of moderately severe symptoms.
The study analyzed anonymized national health data covering 1.37 million pregnancies from 2005 to 2019 and revealed an overall fivefold increase in anti-nausea medication use during pregnancy, rising from 4.1% to nearly 20%. Dr. Donald highlighted that nausea and vomiting affect up to 70% of pregnancies and noted the historically under-recognized impact these symptoms can have on women, which likely contributed to the rise in treatment rates.
While ondansetron is considered an effective treatment, concerns remain regarding its safety during pregnancy. Some previous studies have suggested a possible, albeit very small, increased risk of certain birth defects associated with first-trimester exposure, including heart defects and cleft lip or palate. However, other research has not found a clear link, leaving the evidence inconclusive.
Dr. Donald emphasized that most data do not indicate a major safety concern but acknowledged that the possibility of a slight increased risk has not been definitively ruled out. She cautioned that widespread use could potentially lead to a greater number of affected infants, even if the individual risk remains very low. Consequently, she called for further investigation to clarify the safety profile of ondansetron during early pregnancy.
Her research team is currently examining whether ondansetron use in early pregnancy correlates with adverse pregnancy outcomes. In the meantime, Dr. Donald advised women to continue using the medication if prescribed and stressed that there is no reason for panic based on current information.