Is It Safe To Take Zofran During Pregnancy? Risks And Dosage

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Zofran (a brand name for Ondansetron) is an antiemetic drug that helps ease nausea and vomiting. Its off-label use (the use of a drug for a condition not specified on its label by the FDA) to treat pregnancy-induced morning sickness is common. But is Zofran during pregnancy a safe choice?

Knowing this is crucial as the US Food And Drug Administration (FDA) only approves using Zofran to cease nausea and vomiting caused by chemotherapy, radiotherapy, or surgery. The drug functions by blocking the serotonin receptors (5HT3) and hormones that trigger nausea and vomiting (1).

Keep reading to know more about the safety, risks, and side effects of using Zofran during pregnancy.

Is It Safe To Take Zofran When Pregnant?

Zofran is usually safe for use during pregnancy. There has been an increase in the use of Ondansetron among pregnant women during their first trimester for treating morning sickness. The Centers for Disease Control and Prevention (CDC) states that Ondansetron does not increase the risk of birth defects when used early in pregnancy. However, you should consult your obstetrician-gynaecologist (OB-GYN) if you wish to use Zofran or any medication for nausea, vomiting, or morning sickness during pregnancy (2).

Why Would A Doctor Prescribe Zofran?

Your doctor may prescribe Zofran to help reduce severe symptoms of morning sickness. Nausea and vomiting in pregnancy are common, especially during the first trimester. Mild cases may resolve spontaneously or require some dietary and lifestyle modifications.

However, some women experience severe symptoms leading to dehydration, weight loss, and other complications. The condition is termed hyperemesis gravidarum (HG) that may need medications for management (3). The FDA-approved combination of Doxylamine and Pyridoxine (vitamin B6) is used as a first-line treatment. The second-choice drugs include antihistamines and dopamine blockers (diphenhydramine, promethazine). Ondansetron is advised when patients show little improvement from the previous two regimens. However, due to its efficacy, Ondansetron has been identified as the most commonly prescribed antiemetic in the US (4) (5).

What Are The Risks Of Using Zofran During Pregnancy?

Most of the studies on the use of Zofran during pregnancy have not found significant risks of using the medication. However, there are a few exceptions. A study on 88,467 pregnant women exposed to Ondansetron during the first trimester of pregnancy found a small increase in the risk of oral cleft (cleft palate) in the newborn (6).

A few other studies have identified an increased risk of kidney problems and heart defects (septal defects) in the baby. However, the majority of these studies had a small sample size. Further clinical research is required to confirm the results (7).

The FDA advises exercising precautions while using Zofran in persons with heart disorders as the drug may cause heart problems, such as increased heartbeat rate (tachycardia). You should inform your doctor about any underlying heart conditions or family history of cardiac issues (1).

What Is The Prescribed Dose Of Zofran In Pregnancy?

Zofran is available as orally disintegrating tablets (dissolves in mouth), syrup, wafers, suppositories, and injection. Ondansetron can be given in doses up to 8mg, three to four times per day, usually 4mg should be enough. Zofran is not FDA-approved for pregnancy nausea or HG, so the manufacturer does not provide dosage instructions for them. Therefore, you must consult a doctor to learn the precise dosage of Zofran during pregnancy (8) (9).

What Are The Side Effects Of Zofran?

Side effects of Zofran or Ondansetron may include (10):

  • Headache
  • Weakness
  • Fatigue
  • Chills
  • Drowsiness

Zofran may cause some serious side effects that may require prompt medical attention (1).

  • Allergic reactions such as rash, itching, swelling in the face, hands, or feet, and difficulty breathing.
  • Overdose may cause blurred vision or sudden but temporary blindness.

Serotonin syndrome is a potentially fatal side effect, which may occur if you have Zofran with other drugs that affect serotonin levels. The symptoms of serotonin syndrome may include:

  • Hallucination or delirium
  • Agitation
  • Body tremors
  • Muscle incoordination and rigidity
  • Increased heartbeat rate
  • Fever
  • Coma

What Precautions Should You Take When Using Zofran During Pregnancy?

You should take certain precautions while taking Zofran during pregnancy (1).

  • Inform your doctor about all medications you are taking. Drugs such as selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors, mirtazapine, and lithium may produce serotonin syndrome if co-administered with Zofran.
  • Avoid taking any over-the-counter medications without consulting your doctor.
  • Zofran is usually avoided if dehydration and electrolyte imbalance occurs due to severe vomiting.
  • Ondansetron is contraindicated in persons with congenital (present at birth) long QT syndrome (increases risk of arrhythmias).
  • Report all adverse effects to your healthcare provider.

Zofran (Ondansetron) is effective in treating nausea and vomiting of pregnancy and is usually considered safe.

However, it is not known fully known if Ondansetron increases the risk of birth defects in newborns. Talk to your OB-GYN if you wish to have Zofran or other antiemetic medication during pregnancy.

Key Pointers

  • Zofran is the class of medications used to relieve symptoms of nausea and vomiting post-chemotherapy, surgery, and radiotherapy.
  • According to the CDC, the drug is generally safe to consume during the early weeks of pregnancy to cope with morning sickness.
  • Although rare, Zofran may increase the risks of fetal complications such as oral cleft and kidney or heart problems in the baby.
  • To prevent any serious side effects, consult your doctor about the right dosage and inform them about any ongoing medications or underlying conditions to avoid adverse reactions.


MomJunction's articles are written after analyzing the research works of expert authors and institutions. Our references consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.
  1. Zofran.
  2. Taking Ondansetron During Pregnancy Does Not Appear to Increase Risk For Birth Defects.
  3. Lindsey K. Jennings and Heba Mahdy; (2021); Hyperemesis Gravidarum.
  4. Ondansetron (Zofran) for Nausea and Vomiting in Pregnancy: Maybe Not for All Women.
  5. Amy Abramowitz et al.; (2017); Treatment options for hyperemesis gravidarum.
  6. Krista F. Huybrechts; (2019); Association of maternal first trimester ondansetron use with cardiac malformations and oral clefts in offspring.
  7. Samantha E. Parker et al.; (2018); Ondansetron for Treatment of Nausea and Vomiting of Pregnancy and the Risk of Specific Birth Defects.
  8. Brand name: Zofran.,2471000168108/zofran
  9. Debra Kennedy; (2016); Ondansetron and pregnancy: Understanding the data.
  10. Ondansetron.
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Dr. Karla S. Sanchez-Banos

Dr. Karla S. Sanchez-Banos is a board-licensed Ob/Gyn in Mexico, specializing in Adolescent Gynecology. She is also trained in Gynecological Endocrinology, granted by AMEGIN (Gynecological Endocrinology Mexican Association). Her decade-old experience includes scientific research in teen pregnancy and the use of long-acting reversible contraceptive methods in the adolescent age group.  Dr. Karla currently works in two private medical centers in... more

Dr. Joyani Das

Dr. Joyani Das is a PhD in Pharmacology with over two years of experience in academics. Previously, she worked as an associate professor, faculty of Pharmacology. With her research background in preclinical studies and a zeal for scientific writing, she joined MomJunction as a health writer. Her research work was published in international journals and publications, such as Elsevier, Current... more