Healthy pregnancy hub

Ondansetron (Zofran®)

Last Update: 08 Apr 2025

Welcome to our fact sheet on ondansetron (Zofran®) during pregnancy and breastfeeding/ chestfeeding. This information is based on available published literature. It should not take the place of medical care and advice from your healthcare provider.

The HEALTHY PREGNANCY HUB team is collaborating with MotherToBaby to share information on this topic. The original version is available here (updated on April 2024).

Serene, our chatbot, can also answer your questions about medications during pregnancy.

Please note that this fact sheet is based on United States information and has been adapted for Canada, with a review by our Canadian experts. Minor differences may exist between the two countries. Always consult your healthcare professional for information tailored to your situation.

1. What is ondansetron?

Ondansetron is a medication that has been used to treat nausea and vomiting following surgery, chemotherapy, or radiation therapy. Ondansetron has also been prescribed during pregnancy to help with symptoms of nausea and vomiting in pregnancy (NVP). NVP is also referred to as “morning sickness”. A brand name for ondansetron is Zofran®. 

Sometimes when people find out they are pregnant, they think about changing how they take their medication, or stopping their medication altogether. However, it is important to talk with your healthcare providers before making any changes to how you take this medication. Your healthcare providers can talk with you about the benefits of treating your condition and the risks of untreated illness during pregnancy. 

MotherToBaby has a fact sheet on NVP in pregnancy at: https://mothertobaby.org/fact-sheets/nausea-vomiting-pregnancy-nvp/. 

2. What are the risks according to research?

I take ondansetron. Can it make it harder for me to get pregnant?

It is not known if taking ondansetron can make it harder to get pregnant. Animal studies did not find that ondansetron affects the ability to get pregnant. 

Does taking ondansetron increase the chance for miscarriage?

Miscarriage is common and can occur in any pregnancy for many different reasons. Studies have not reported a higher chance of miscarriage with use of ondansetron in pregnancy. 

Does taking ondansetron increase the chance of birth defects?

Birth defects can happen in any pregnancy for different reasons. Out of all babies born each year, about 3 out of 100 (3%) will have a birth defect. We look at published data to try to understand if an exposure, like ondansetron, might increase the chance of birth defects in a pregnancy. A few studies reported a less than 1% (less than 1 in 100) increase in the chance for a cleft palate (an opening in the roof of the mouth that can be repaired with surgery) or a heart defect. Other studies have not confirmed these findings. Most studies have not reported an increased chance for birth defects among thousands of individuals who used ondansetron in pregnancy. 

Does taking ondansetron in pregnancy increase the chance of other pregnancy-related problems?

Studies did not find a higher chance of pregnancy loss, preterm delivery (delivery before 37 weeks of pregnancy), or low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth) when ondansetron was used during pregnancy. 

When taken at high doses, there have been reports that ondansetron might cause a heart rhythm problem (called QT interval prolongation) in the person taking ondansetron. In severe cases, this could become an abnormal heart rhythm known as Torsades de Pointes. If you are taking ondansetron, talk to your healthcare provider about your dose and how to watch for changes in your heart rhythm. 

Does taking ondansetron in pregnancy affect future behavior or learning for the child?

One study looked at 78 infants who were exposed to ondansetron at any time during pregnancy. When examined between 7 days to 2 months of age, there were no unusual behaviors reported. A single follow-up survey asking about behavior was sent in by parent of about 25 of these children. The children were between 1½ years to 5½ years old. No behavior differences were reported in these children compared to children who were not exposed to ondansetron during pregnancy. 

3. Breastfeeding/ chestfeeding while taking ondansetron

Information on the use of ondansetron during breastfeeding/ chestfeeding is limited. Side effects in breastfeeding/ chestfeeding infants have not been reported. Ondansetron has been given directly to infants as young as 1 month of age. Be sure to talk to your healthcare provider about all your breastfeeding/ chestfeeding questions. 

4. Fathers and sperm donors

If a male takes ondansetron, could it affect fertility or increase the chance of birth defects?

Studies have not been done to see if ondansetron could affect a male’s fertility (ability to get a partner pregnant) or increase the chance of birth defects above the background risk. Animal studies have not shown any effect on a male’s fertility. In general, exposures that fathers and sperm donors have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures here.   

Key points

  • Ondansetron (Zofran®) is a medication used to treat nausea and vomiting after surgery, chemotherapy, or radiation therapy, as well as nausea and vomiting during pregnancy (NVP).
  • Most research has not found an increased risk of birth defects among the thousands of people who have taken ondansetron during pregnancy. Studies have not found a higher risk of miscarriage, preterm birth (before 37 weeks of pregnancy), or low birth weight (less than 5 pounds, 8 ounces [2,500 grams]).
  • At high doses, ondansetron may carry a risk of abnormal heart rhythm (Torsades de Pointes) in the person taking it.
  • There is limited information on breastfeeding/ chestfeeding, but no side effects have been reported in nursing babies.
  • No studies have been done to determine whether ondansetron affects male fertility or increases the risk of birth defects beyond the background risk.
  • Always consult your healthcare team before changing your treatment during pregnancy or breastfeeding/ chestfeeding.

References

Please click here for references. 

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Disclaimer

HEALTHY PREGNANCY HUB provides a source of information validated by health professionals; however, this information is provided for informational purposes only and should not replace professional advice. Medical standards and practices evolve as new data becomes available, so it is imperative to consult your doctor or a qualified health professional for any questions or concerns regarding your health without delay or omission. It is the responsibility of your treating physician or any other health professional, based on their independent experience and knowledge of the patient, to determine the best way to evaluate and treat you.

HEALTHY PREGNANCY HUB does not specifically recommend or endorse any test, practitioner, treatment, product, or opinion mentioned on our platform. HEALTHY PREGNANCY HUB also does not replace the individual patient assessment based on the examination by the healthcare provider of each patient and the consideration of laboratory data and other patient-specific factors.

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While consulting symptoms or other medical information on our platform may guide your discussions with your healthcare professional, this information should not be used to make a medical diagnosis or determine treatment. Before making changes to your supplement or medication regimen, please discuss with your medical team or contact 811 (Canada) to ensure the relevance of these changes to your individual situation.

Credits
MotherToBaby
Organization of Teratology Information Specialists (OTIS)
View source
Émy Roberge
Centre hospitalier universitaire Sainte-Justine
Anne-Sophie Otis
Centre Hospitalier Sainte-Justine

Associated Fact Sheets

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Associated Resources

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