Birth defects linked to the use of Zofran during the first trimester of pregnancy include heart defects, cleft palate, and more.

Zofran and Birth Defects

Zofran (ondansetron) is an anti-nausea drug manufactured by GlaxoSmithKline (GSK). Since the 1990s, it has been used “off-label” to treat morning sickness in pregnant women. This use is not approved by the FDA.

In recent years, several studies have found that Zofran crosses the placenta in “significant amounts,” passes very quickly from mother to fetus, and remains active in the fetus much longer than it does in the mother. This raises concern about the risk of birth defects.

In August 2013, Dr. Jon A. Anderson presented data from a study of nearly 900,000 pregnancies in Denmark between 1997-2010. He found that women who used Zofran were 30% more likely to have a baby with a birth defect, and twice as likely to have a baby with a heart defect.

Out of 1,250 women who used Zofran, nearly 5% had a baby with a birth defect, compared to 3.5% of women who did not use Zofran. In the general population, the baseline risk for heart defects is 1-2%.

Interestingly, six months earlier, the New England Journal of Medicine published another study based on 600,000 births from the same registry of pregnancies in Denmark, but found no evidence linking Zofran and birth defects.

However, the average woman took Zofran at the 10th week of pregnancy, meaning that half of the fetuses were exposed to Zofran after they were no longer at risk of major malformations, including heart defects and cleft lip/palate.

At least two other recent studies have linked Zofran and birth defects, including:

Heart Defects

Case reports link Zofran and the following heart defects:

  • Atrial Septal Defect (ASD): This defect is a hole in the wall between the two upper chambers (“atria”) of the heart. The hole increases the amount of blood that flows to the lungs. Over time, delicate blood vessels in the lungs can be damaged and life-threatening complications can occur.
  • Ventricular Septal Defect (VSD): This is a hole in the wall between the two lower chambers (“ventricles”) of the heart. If the hole is large, oxygen-rich blood can mix with oxygen-poor blood and cause complications.
  • Heart Murmur: This is any abnormal sound that a doctor hears when listening to the baby’s heart with a stethoscope. Although most heart murmurs are harmless, they may be a sign of a heart defect.

Zofran Linked to 2X Risk of Cleft Palate and Cleft Lip

In January 2012, Birth Defects Research published a study linking the use of Zofran during pregnancy with a 2.4-fold increased risk of cleft palate, based on data from over 9,000 pregnancies. Conclusions were reported by the Sloan epidemiology unit and the Centers for Disease Control (CDC), based on data from the National Birth Defects Prevention Study.

What is Cleft Palate?

Cleft palate is a birth defect that occurs when the roof of the baby’s mouth does not grow properly. All fetuses start development with cleft palate, but tissue normally closes the gap around the 10th week of pregnancy.

Cleft palate may involve the hard palate, soft palate, or both. In severe cases, the defect extends into the nose, through the gums, and connects to a cleft lip. Many children with this birth defect need to be fed with a bottle because they have trouble forming suction on a breast and swallowing. They may also need multiple corrective surgeries within the first few years of life.

What is Cleft Lip?

Cleft lip is a birth defect that causes a gap in the baby’s upper lip. It may occur on one or both sides, or in the middle of the lip. Mild cases involve only a tiny notch. Severe case connect to the nose and a cleft palate. It typically occurs around the 7th week of pregnancy. Cleft lip can interfere with feeding, but with careful management and surgery, long-term prognosis for babies with cleft lip is very good.

Investigation Links Zofran and Birth Defects

Evidence linking Zofran and birth defects continued to increase in June 2014, when the Toronto Star published an investigative report on 20 women from Canada who had a baby with a birth defect after using Zofran during pregnancy, including:

  • Multiple reports of heart defects and kidney malformations.
  • Musculoskeletal abnormality
  • One baby had a mouth deformity, jaundice, heart murmur, and two heart defects (atrial septal defect, also known as a “hole in the heart”)
  • Fetal growth restriction, including four babies who weighed as little as 4.5 pounds at birth
  • Two fetal deaths


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