New study findings offer reassurance to pregnant women that acetaminophen does not appear to raise the risk of birth defects.
Acetaminophen is the active ingredient in Tylenol and certain other painkillers, and is often found in over-the-counter cold and flu remedies. Taken as directed, acetaminophen is considered safe during pregnancy, making it the medication of choice for pregnant women's body aches and fevers.
However, there are still some questions about whether the drug can contribute to birth defects. Studies looking at birth defects as a broad group have either found no link to acetaminophen use or have yielded inconclusive findings.
Some research, meanwhile, has suggested that the drug may be linked to a higher risk of a birth defect called gastroschisis—but other studies have found no such connection. Gastroschisis refers to a defect in the abdominal wall that allows the intestines to protrude; it has been linked to aspirin use during pregnancy.
In the new study, researchers analyzed data from a large U.S. study that included more than 11,600 children born with congenital defects such as spina bifida, cleft lip and various defects affecting the brain, heart, lungs, limbs and gastrointestinal system. They were compared with 4,500 children born with no major anomaly.
Overall, the study found, there was no evidence linking mothers' acetaminophen use in the first trimester to a heightened risk of any birth defect.
In fact, women who took the medication to treat a first-trimester fever had a lower risk of certain birth defects—including gastroschisis—than women who did not treat their fevers with acetaminophen.
Researchers led by Dr. Marcia L. Feldkamp, of the University of Utah in Salt Lake City, report the findings in the January 2010 issue of the journal Obstetrics & Gynecology.
The findings, according to the researchers, show that there is "little evidence that single-ingredient acetaminophen increases the risk of a broad range of birth defects."
They also raise the "intriguing" possibility that lowering a first-trimester fever with acetaminophen cuts the risk of certain defects, Feldkamp's team writes.
Among women who had fevers in early pregnancy, babies born to those who used acetaminophen had a 65 percent to 83 percent lower risk of certain birth defects of the brain, a 56 percent lower risk of cleft lip and a 59 percent lower risk of gastroschisis.
The researchers note that hyperthermia, or excessively high body temperature, has been implicated in the risks of certain birth defects. More studies, they conclude, are needed to confirm whether treating fevers with acetaminophen does in fact prevent some birth defects.
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