During the first trimester of pregnancy, taking Zofran to prevent morning sickness may double the risk of having a baby with a heart defect, according to two recent studies.
Zofran Heart Defect Information
August 2013 — The risk of heart defects is twice as high for babies who are exposed to Zofran (ondansetron) during the first trimester of pregnancy, according to the study “Ondansetron use in early pregnancy and the risk of congenital malformations.”
Zofran is a powerful anti-nausea drug that is not approved by the FDA for morning sickness.
Conclusions of the study were based on a data from nearly 900,000 pregnancies in Denmark between 1997 and 2010. About 1,250 women reported using Zofran during the first three months of pregnancy, including 58 (4.7%) who had a baby with a birth defect.
The rate of birth defects was 30% higher for women who used Zofran compared to women who did not, mostly due to a 2-fold increased rate of heart defects.
To rule out other risk-factors that may have confounded the results, researchers also looked at the risk of birth defects from metroclopramide, another anti-nausea drug. No risk of birth defects was found.
Study Finds Zofran Doubles Risk of “Hole in the Heart” Defects
A study published by Reproductive Toxicology in December 2014 found that Zofran doubled the risk of septal heart defects (also known as “hole in the heart” defects. The conclusions were based on data from the Swedish Medical Birth Register, including 1,349 infants exposed to Zofran in early pregnancy from 1998-2012.
Case Reports Link Zofran and Heart Defects
An investigation published by the Toronto Star in June 2014 reported at least 20 cases of birth defects associated with Zofran, including multiple reports of heart defects. One baby had a “hole in the heart” (atrial septal defect) and a heart murmur. Click here to read more.
Not all babies who have a heart murmur have a heart defect, although it can be the first symptom. The “murmur” can actually be a clicking, whooshing, or other abnormal sound heard using a stethoscope.
Atrial and Ventricular Septal Defects
Every fetus begins development with holes in the walls that separate four chambers of the heart. In the womb, holes are harmless because the baby receives oxygen-rich blood from its mother. The holes normally close before the baby is born or shortly afterward.
“Hole in the heart” defects are also known as:
- Atrial septal defect: Hole in the septal wall between the upper-left and upper-right chambers of the heart (“atria”)
- Ventricular septal defect: Hole in the septal wall between the lower-left and lower-right chambers of the heart (“ventricles”)
What is the problem?
Major circulation problems can occur when a baby has a large atrial or ventricular septal defect. Normally, oxygen-depleted blood from the body goes through the right side of the heart, into the lungs where it receives oxygen, and oxygen-rich blood is pumped through the left side of the heart into the body.
When there is a hole, oxygen-depleted blood mixes with oxygen-rich blood, resulting in oxygen-poor blood being pumped into the body. Infants may fail to thrive, grow, and develop normally.
Over time, a septal defect can cause pulmonary hypertension (high blood pressure in the lungs). This can also increase the risk of bacterial endocarditis (bacterial infections in the heart), heart failure, and death.
Symptoms of a Heart Defect
- Heart murmur
- Failure to thrive
- Shortness of breath, hard or rapid breathing
- Cyanosis (“blue baby syndrome”)
- Rapid heartbeat
- Sweating while feeding