March 18, 2015 — Using Zofran during pregnancy could double the risk of having a baby with a heart defect, according to a study published late last year by Swedish researchers in the journal Reproductive Toxicology.
The researchers looked at data from the Swedish Medical Birth Register, combined with another registry of prescribed drugs. They identified 1,349 infants who were exposed to Zofran during early pregnancy between 1998 and 2012.
There was no statistically significant increase in major birth defects overall. However, Zofran was associated with a 62% increased risk of heart defects, including a doubled increased risk of “hole in the heart” defects (also known as cardiac septum defects).
The researchers warned:
“[I]f an association between the use of ondansetron and an increased risk for cardiovascular defects is true, the strongly increasing off label use of the drug at nausea and vomiting in early pregnancy must be regarded as unsuitable and should be avoided.”
In the general population, about one in every 100 babies is born with a congenital heart defect. Researchers concluded that the birth defect risk from Zofran was “low,” but “an increased risk for a cardiac septum defect is likely.”
Septal defects include atrial septal defect and ventricular septal defect.
Normally, the heart separates into four chambers in the first few weeks of pregnancy. A wall called a septum divides the two upper chambers (“atria”) and two lower chambers (“ventricles”). If the septum does not form completely, the baby is born with a heart defect.