Zofran

THE SAFETY OF ZOFRAN (ONDANSETRON) DURING PREGNANCY OR BREASTFEEDING

The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.

THIS MEDICATION CAN CAUSE HARM TO YOUR BABY:
Zofran (ondansetron) should only be used during pregnancy if medically necessary, as determined by your doctor. Some studies have associated the use of ondansetron during pregnancy with a higher risk of major birth defects, birth defects in the heart, cleft palate, and kidney abnormalities.

What is Zofran (ondansetron)?

Zofran (ondansetron) is used to prevent nausea and vomiting. The active ingredient in Zofran is ondansetron. It is available as tablets, orally disintegrating tablets, liquid, and an injectable solution. Ondansetron is only available by prescription.

What is Zofran (ondansetron) used to treat?

Ondansetron is used to prevent nausea and vomiting caused by chemotherapy, radiation therapy, and surgery. Occasionally, healthcare professionals prescribe ondansetron off-label to treat nausea and vomiting during pregnancy. About 50% to 90% of expecting moms experience nausea, either with or without vomiting. Mild nausea and vomiting during pregnancy is often referred to as morning sickness and usually develops within 5 to 6 weeks of conception. The severity and length of morning sickness symptoms can differ. Most expecting moms experience nausea and vomiting during the first trimester, but some may have symptoms that last until delivery. Expecting moms who experience more severe nausea and vomiting, called hyperemesis gravidarum, typically require hospitalization and treatment to prevent harm to the mom and baby. You can read more about nausea and vomiting during pregnancy here and ways to manage nausea and vomiting here.

How does Zofran (ondansetron) work?

Ondansetron blocks the action of serotonin, which is a natural chemical in your body that can cause nausea and vomiting. 

If I am taking Zofran (ondansetron), can it harm my baby?

Ondansetron should only be used during pregnancy if medically necessary, as determined by your doctor. This medication crosses the human placenta to reach the developing baby, and could harm your baby. Some studies have associated the use of ondansetron during pregnancy with a higher risk of birth defects. Your doctor will determine if ondansetron is medically necessary, or if it should be discontinued during pregnancy. You can read about the risks of Zofran during pregnancy here.

Evidence:

The Centers for Disease Control and Prevention (CDC) collaborated with the Slone Epidemiology Center at Boston University on a study that analyzed data from the National Birth Defects Prevention Study (1997-2011) and the Slone Birth Defects Study (1997-2014). The study looked at data from 35,824 expecting moms and did not find a higher risk of most birth defects with the use of ondansetron during pregnancy. A slightly increased risk of some birth defects, including cleft palate and abnormal kidney development or absence of one or both kidneys, was observed. Due to the increased risk of certain birth defects that was observed, the authors concluded that more studies are needed to determine the safety of ondansetron during pregnancy.

A study published in the New England Journal of Medicine looked at pregnancy outcomes from 2004 to 2011 in 608,385 expecting moms from the Medical Birth Registry and National Patient Register in Denmark. The use of ondansetron during pregnancy was not associated with a higher risk of any major birth defect, miscarriage, stillbirth, or low birth weight. Some experts were concerned about the conclusions reached in this study because half of the expecting moms who were exposed to ondansetron took the medication after 10 weeks of pregnancy, which is beyond the period when a drug can cause a birth defect. 

Another study reanalyzed data from the registries used in the previously mentioned study (Medical Birth Registry and National Patient Register in Denmark). This study looked at birth outcomes for a longer period of time (from 1997 to 2010) and included more expecting moms (897,018). The study found that moms who took ondansetron during the first trimester of pregnancy had a 2 times higher risk of birth defects in the heart and an overall 30% higher risk of major birth defects.

A study looked at pregnancy outcomes from 1998 to 2012 in 1349 expecting moms who took ondansetron early in pregnancy using data from the Swedish Medical Birth Register and the Swedish Register of Prescribed Drugs. The study did not find a significantly higher risk of major birth defects, but a higher risk of birth defects in the heart was observed.

Due to the uncertainties regarding the safety of ondansetron during pregnancy, some authors have suggested that ondansetron should not be considered a first-line medication for the treatment of nausea and vomiting in pregnancy. 

Bottom line: Ondansetron should only be used during pregnancy if medically necessary, as determined by your doctor. A higher risk of major birth defects, birth defects in the heart, cleft palate, and kidney abnormalities have been observed in some studies.

If I am taking Zofran (ondansetron) and become pregnant, what should I do?

If you become pregnant while taking ondansetron, you should contact your doctor immediately. Your doctor will determine if ondansetron is medically necessary, or if an alternative should be prescribed.

If I am taking Zofran (ondansetron), can I safely breastfeed my baby?

Caution should be used if ondansetron is taken by breastfeeding moms. Your doctor will evaluate the potential risks of ondansetron exposure to your baby and determine if treatment with ondansetron is medically necessary. Ondansetron has been shown to pass into breast milk in rats, but it is unknown if the medication passes into breast milk in humans. No reports or studies have described the effects of ondansetron exposure on the breastfed baby. Due to the lack of data, an alternative medication may be recommended for breastfeeding moms.

Bottom line: Caution should be used in breastfeeding moms who are taking ondansetron. It is unknown if ondansetron passes into human breast milk, and its effects on the breastfed baby have not been studied.

If I am taking Zofran (ondansetron), will it be more difficult to get pregnant?

No studies have looked at the effects of ondansetron on human fertility. Animal studies did not observe any changes in fertility in male or female rats at 6 times the maximum recommended human dose.

If I am taking Zofran (ondansetron), what should I know?  

Ondansetron should only be used during pregnancy if medically necessary, as determined by your doctor. This medication crosses the human placenta and could cause harm to your baby. Some studies have observed a higher risk of major birth defects, birth defects in the heart, cleft palate, and kidney abnormalities with the use of ondansetron during pregnancy.

Caution should be used if ondansetron is taken by breastfeeding moms. It is unknown if ondansetron passes into breast milk, and the effects on the breastfed baby have not been studied.

If I am taking any medication, what should I know?

This report provides a summary of available information about the use of Zofran (ondansetron) during pregnancy and breastfeeding. Content is from the product label unless otherwise indicated.

You may find Pregistry's expert report about nausea and vomiting here and reports about the individual medications used to treat digestive system disorders here.   Additional information can also be found in the resources below. 

For more information about Zofran (ondansetron) during and after pregnancy, contact http://www.womenshealth.gov/ (800-994-9662 [TDD: 888-220-5446]) or check the following links:

Mayo Clinic :Ondansetron (Oral Route, Oromucosal Route) 

Centers for Disease Control and Prevention: Taking Ondansetron During Pregnancy Does Not Appear to Increase Risk For Birth Defects.

Read the whole report
Last Updated: 27-02-2019
General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.