Women who use the anti-nausea drug Zofran to treat morning sickness during the first trimester may be twice as likely to have a baby with a heart defect, including “hole in the heart” defects or a heart murmur, according to two recent studies.

Zofran and Heart Defects

December 2014 — Reproductive Toxicology a study concluding Zofran doubled the risk of “hole in the heart” defects (septal defects). The study was conducted by researched in Sweden and results were based on data from 1,349 infants whose mothers took Zofran in early pregnancy from 1998-2012.

August 2013 — The use of Zofran during the first trimester of pregnancy was linked to a doubled risk of heart defects in a large study titled “Ondansetron use in early pregnancy and the risk of congenital malformations.”.

The study included all women who gave birth in Denmark between 1997 and 2010, with approximately 897,000 births in the study period. Of the 1,248 women who used Zofran in the first trimester, 58 (4.7%) had a baby with a birth defect compared to 3.5% of women who did not use Zofran.

Zofran increased the risk of birth defects by 30% overall, mostly due to the increased number of heart defects.

To rule out confounding factors, the researchers also looked at another drug commonly used to treat pregnant women with morning sickness — metroclopramide — but found no evidence of birth defects in the first trimester.

Investigation Links Zofran and Heart Defects

In June 2014, the Toronto Star investigated 20 reports of Canadian women who had babies with birth defects after using Zofran. Multiple reports involved heart defects. One baby had a heart murmur and two heart defects, including an atrial septal defect (“hole in the heart”). Click here to read more.

What is a Heart Murmur?

A heart murmur is any extra or unusual sound that is heard when listening to the heart with a stethoscope. It can be a symptom of a heart defect, with different defects producing different sounds, but most heart murmurs are harmless. Innocent heart murmurs do not cause symptoms and do not need treatment.

“Hole in the Heart” Defects

In the womb, the heart develops with holes between the upper and lower chambers. These holes are not a problem during fetal development, when the baby receives oxygen from the mother. However, they normally close before the baby is born or within the first few weeks of life.

If the holes do not close, the baby has one of the following heart defects:

  • Atrial septal defect is a heart defect that occurs when there is a hole in the wall (“septum”) that separate the two upper chambers of the heart (“atria”).
  • Ventricular septal defect causes a hole in the wall between the two lower chambers of the heart (“ventricles”).

Failure to Thrive

Normally, the left and right sides of the heart are separated by the septal wall. When there is a hole, oxygen-rich blood mixes with oxygen-depleted blood, resulting in low oxygen levels in the blood that goes to the body. In infancy, this delays growth and development.


Very large holes in the heart will cause too much blood to be pumped into the lungs. Over time, this damages delicate blood vessels in the lungs, resulting in pulmonary hypertension (high blood pressure in the lungs). It can also lead to bacterial infections in the heart, heart failure, and death.


  • Shortness of breath
  • Fast breathing
  • Paleness
  • Failure to gain weight
  • Fast heart-rate
  • Sweating while feeding


Small holes in the heart often close on their own and need no treatment, through the baby should be closely monitored to make sure the hole closes properly. They may need medication to control symptoms and surgery to close the hole. Surgery typically involves implanting a small patch.


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