Is Zofran (Ondansetron) Safe for Pregnancy?

Zofran medication during pregnancy
Medically reviewed by Dr. Ola Tarabzuni

Key Takeaways

  • Zofran (Ondansetron) offers a safe solution for managing severe pregnancy-related nausea. It effectively alleviates symptoms without posing significant risks to the well-being of both the mother and the developing fetus.
  • While there is a potential for birth defects, studies show that the occurrence of such defects due to Zofran use during pregnancy is rare. 
  • Most cases have reported no adverse effects, reassuring expectant mothers about the medication’s safety.

Zofran, an Ondansetron prescription drug, helps manage severe pregnancy nausea and is prescribed by healthcare providers to combat early pregnancy nausea. It’s safe, with minimal risks to both mother and baby. Birth defects are less likely to happen but can’t be avoided altogether. Common side effects include headaches and drowsiness.

Consult your healthcare provider before taking Zofran (ondansetron) while pregnant, especially in the first trimester. Zofran crosses the placenta and reaches the baby having its effects. A black box warning indicates potential heart-related risks. Stick to prescribed doses, eg, 4mg of Zofran in pregnancy, to avoid unwanted adverse effects. Zofran 4mg in pregnancy starts working in about 20-30 minutes and will reach its maximum effects in 2 hours. It is not an over-the-counter medication and can only be dispensed by prescription.

What Is Zofran?

Zofran is the brand name for the drug Ondansetron belonging to the class of 5H3 Serotonin Antagonists. This class of drugs is used and prescribed to cease the effect of the serotonin hormone, which generally is responsible for mood fluctuations, sleeping cycles, nausea, appetite, anxiousness, blood aggregation, and sexual desire.

Antagonizing the serotonin hormone will decrease mood swings and nausea accompanied by vomiting. These drugs significantly impact the changes after chemotherapy and reduce cyclic episodes of vomiting.

It is available in different dosage forms as an

  1. Injectable solution of 2mg/mL,
  2. Oral tablets of (4mg,8mg,24mg) and
  3. Oral solutions of 4mg/5mL.
Get Zofran Medications For Nausea and Vomiting in Minutes

Why Is Ondansetron Used In Pregnancy?

Ondansetron (Zofran) is used during pregnancy to control nausea and vomiting, which is generally termed hyperemesis gravidarum during the first trimester of pregnancy. It often is taken after or with meals to increase its effectiveness. It’s also good to take it right at the time when feeling nauseous because of its rapid onset of action. 

No doubt, pregnancy comes with many distressing symptoms during the first two trimesters, including hyperemesis gravidarum, which is defined as a “severe form of morning sickness that can lead to antiperistalsis (emesis)  more than a few times in a day altogether.”

Other uses of Ondansetron from pregnancy is it is prescribed for the management of after-effects following post-operative conditions, chemotherapy, and radiation therapies.

Can You Take Zofran While Pregnant?

Yes, Zofran is safe for pregnancy or categorized as low-risk medicine to be taken while pregnant for pregnancy-related nausea, and studies show zero to few effects of ondansetron (Zofran-4mg) on the health of the bearing mother as well as the developing fetus.

Stopping the prescribed ondansetron (Zofran) after the first trimester is safe, and it’s good to talk to your healthcare provider before continuing it after early pregnancy to avoid any unwanted side effects. 

As per the article published by The National Institutes of Health (NIH), most of the independent studies conducted altogether have not reported a chance of birth defects among thousands of bearing mothers who used ondansetron during pregnancy.

Zofran has received approval from the Food and Drug Administration (FDA) for its use in combating nausea after chemotherapy but not specifically for managing morning sickness in pregnancy.

Pyridoxine (vitamin B6) therapy is often prescribed as FDA approved drug for managing nausea during pregnancy in the dose of 10 to 25 mg orally every six to eight hours, as needed.

The doxylamine-pyridoxine combination is also approved if pyridoxine alone doesn’t work.

What Birth Defect Does Zofran Cause?

Even with the lower and decreased chances of birth defects after consuming Zofran, some that are observed are

1. Heart defects 

2. Cleft palate

3. Skull deformities

In February 2015, a mother from Minnesota initiated the initial legal action against Zofran, filing a lawsuit when her two daughters were born with congenital heart anomalies. Subsequently, other cases swiftly emerged, including instances of an absent kidney in a child and the occurrence of a cleft palate.

Some of the other side effects of taking Zofran 4mg tablets during pregnancy are as follows:

1. Headaches.

2. Feeling drowsy.

3. Experiencing lightheadedness.

4. Constipation.

5. Infrequent occurrences may lead to:

                       Irregular heartbeats (QT-prolonging).

                       Elevated serotonin levels, which could potentially be life-threatening.

Each pregnancy generally commences with a baseline risk of 2-5% for potential birth defects, which is referred to as the background risk.

What Nausea Medicine Is Safe While Pregnant?

The Doxylamine-pyridoxine combination is approved by the FDA for combating pregnancy-related nausea and vomiting as safe for vulnerable fetuses.

The typical dose starts with two extended-release tablets (Diclegis/Bonjesta). Each tablet contains doxylamine 10 mg and pyridoxine 10 mg at bedtime.

What not to do after taking Zofran? Speak with Online Doctor

Consult a Doctor

Pregnancy is the most vulnerable state for a female, especially regarding self-medication. It’s crucial to seek medical guidance at every step during pregnancy before consuming any medication to avoid any chance of impaired abnormalities in the baby. It’s essential to get medical attention from your healthcare provider before starting any prescription drug.

FAQs About Ondansetron in Pregnancy

Does Zofran cross the placenta?

Yes. Zofran (ondansetron) readily crosses the placenta and can reach the developing fetus. As per NIH, it is found that ondansetron rapidly crosses the placental barrier, but it undergoes significantly slower neonatal clearance (clearance from the baby’s body).

What is the black box warning on Zofran?

The black box warning on the packaging of Zofran(ondansetron) indicates the warning sign by the Food and Drug Administration FDA about the side effects of the drug, specifically the risk of the Q wave to T wave time interval (QT) prolongation referring to heart-related abnormalities when taken under different medical conditions.

Why can’t you take Zofran every day?

Zofran 4mg (pregnancy dosage) is prescribed chiefly at the interval of 8 hours, which makes it two to three times a day. If taken more than that, it can cause sudden effects like constipation, dizziness, frontal headache, and changes in heart rhythm. Seeking medical consultation and compliance to only prescribed frequency will benefit.

How long does it take for Zofran to work for morning sickness?

Zofran will take 20 to 30 minutes to start showing its antiemetic and sickness improvement effects. It will maximum take 2 to 2 and a half hours to show its full effects. It largely depends on the dosage form as well. If the dosage form is injectable (100% bioavailability), you will see sudden effects as compared to tablets that are taken orally. It is usually prescribed to take Zofran before mealtime to avoid any nausea-like symptoms.

Your Doctors Online uses high-quality and trustworthy sources to ensure content accuracy and reliability. We rely on peer-reviewed studies, academic research institutions and medical associations to provide up-to-date and evidence-based information to the users.

  • Mother To Baby | Fact Sheets [Internet]. Brentwood (TN): Organization of Teratology Information Specialists (OTIS); 1994-. Ondansetron (Zofran®) 2022 Sep. Available from:
  • Major Congenital Malformation Risk After First Trimester Gestational Exposure to Oral or Intravenous Ondansetron
  • Koren G. Motherisk update. Is ondansetron safe for use during pregnancy? Can Fam Physician. 2012 Oct;58(10):1092-3. PMID: 23064917; PMCID: PMC3470505.
  • Nuangchamnong N, Niebyl J. Doxylamine succinate–pyridoxine hydrochloride (Diclegis) for the management of nausea and vomiting in pregnancy: an overview. Int J Womens Health. 2014;6:401-409
  • Lete I, Alluέ J. The Effectiveness of Ginger in the Prevention of Nausea and Vomiting during Pregnancy and Chemotherapy. Integrative Medicine Insights. 2016;11. doi:10.4137/IMI.S36273
  • Parker, Samantha E. PhD; Van Bennekom, Carla MPH; Anderka, Marlene ScD; Mitchell, Allen A. MD;  for the National Birth Defects Prevention Study. Ondansetron for Treatment of Nausea and Vomiting of Pregnancy and the Risk of Specific Birth Defects. Obstetrics & Gynecology 132(2):p 385-394, August 2018. | DOI: 10.1097/AOG.0000000000002679

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