The study by CDC researchers is published in the American Journal of Obstetrics and Gynecology.
About 4 million babies are born in the U.S. each year. About 3% are born with major birth defects. The most common type of birth defect is a congenital heart defect. More babies die from congenital heart defects in the first year of life than from any other type.
Some previous studies have shown a possible link between codeine and birth defects; the impact of other opioid painkillers has not been thoroughly examined. “The effects of opioid use on the developing fetus during pregnancy are poorly understood,” the researchers write.
Painkillers During Pregnancy
The researchers drew upon data from the ongoing National Birth Defects Prevention Study, focusing on the years 1997 to 2005. They analyzed 17,449 interviews conducted with mothers of infants with birth defects.
In the interviews, the mothers discussed the medications they took during their pregnancy and the three months preceding it. The researchers compared their answers with those of 6,701 mothers of babies born without defects.
Therapeutic opioid use was reported by 2.6% of mothers of babies born with birth defects and by 2.0% of mothers of babies born without birth defects. The study did not examine the use of illicit opioids.
Codeine and hydrocodone were the two most commonly used opioid painkillers among study participants.
Risk of Heart Defects
Opioid drugs were found to raise the risk for several different types of heart defects. This class of medications more than doubled the chances of having a baby born with hypoplastic left heart syndrome. Other birth defects associated with the drugs include spina bifida, congenital glaucoma, and hydrocephaly.
Despite the increased risk, birth defects such as hypoplastic left heart syndrome remain rare, the researchers point out. Still, the risks of opioid use and birth defects should be part of any discussion a woman has with her prescribing doctor, the researchers say.
“With very serious and life threatening birth defects like hypoplastic left heart syndrome, the prevention of even a small number of cases is very important,” says study researcher Cheryl S. Broussard, PhD, of the CDC's National Center on Birth Defects and Developmental Disabilities, in a news release.