Zofran (ondansetron) is not the first choice for pregnancy nausea, but doctors do prescribe it when other options have not worked. ACOG considers it a second-line option, and NHS/UKTIS guidance says to use it only when the benefit clearly outweighs the risk. The main open question is a small possible increase in oral cleft risk with first-trimester use — the evidence is mixed, and this decision belongs with your provider.
Zofran is a brand name for ondansetron, a medicine that blocks nausea and vomiting signals. It was originally developed for chemotherapy and post-surgery nausea. In pregnancy it is prescribed off-label — the FDA has not approved it specifically for morning sickness. Nausea and vomiting affect up to 80% of pregnancies, so the question of what is safe to take is very common.
ACOG recommends ondansetron as a second-line option — after first-line choices like vitamin B6 (pyridoxine) and doxylamine have been tried. The reason for caution is mixed data on first-trimester use: some studies suggest a small possible increase in oral clefts (cleft lip or palate), on the order of a few extra cases per 10,000 exposed pregnancies, while other large studies found no increase above the normal background rate. Because the evidence conflicts, NHS/UKTIS advises using it only when benefits clearly outweigh risks.
Many providers start with non-drug steps and first-line medicines: vitamin B6 (pyridoxine) alone or combined with doxylamine, which ACOG names as first-line and which has a stronger safety record. If nausea is severe or you cannot keep fluids down (possible hyperemesis gravidarum), that is a reason to call your provider promptly rather than wait. If you already took ondansetron before knowing you were pregnant, UKTIS notes this is not usually a reason for extra monitoring or alarm — but tell your provider so they can guide next steps.