In plain words
Ondansetron is a medicine that blocks a chemical signal that triggers nausea and vomiting. Providers use it for severe nausea in pregnancy, and it is also used after surgery and chemotherapy. In pregnancy, it is generally considered after first-line options have been tried. Some studies have reported a small possible increase in oral clefts when it is taken in early pregnancy. Other large studies have not found the same link. The question is still debated. Mothers may be told about this medicine when a provider discusses severe nausea. Whether and how to use it is a decision made with the provider who knows the mother's health.
The deeper version
Ondansetron is a selective 5-HT3 receptor antagonist. Pregnancy guidance from ACOG (Practice Bulletin 189, 2018) places antihistamines and dopamine antagonists in the second tier of treatment for nausea and vomiting, with ondansetron widely used in clinical practice as an off-label option for . Huybrechts et al. (JAMA 2018), in a large cohort, found no increase in overall malformations and a small increase in oral clefts with first-trimester exposure, with an adjusted relative risk near 1.2 that was not seen in every later study. Concern for cardiac malformations has been raised in some studies. Evidence is mostly observational, and confounding by indication is a recognized limitation.
Where it comes up
- Hyperemesis gravidarum: when sickness is severePregnancy: Your Body
- Nausea and vomiting in pregnancyPregnancy: Your Body
- Eating when nothing sounds goodPregnancy: Eating
- Medications and breastfeeding: how to checkFeeding Your Baby
What mothers here say about ondansetron
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Sources
- Huybrechts KF et al. — Association of maternal first-trimester ondansetron use with cardiac malformations and oral clefts in offspring. JAMA 2018
- American College of Obstetricians and Gynecologists — Practice Bulletin 189: Nausea and vomiting of pregnancy, 2018