If you're pregnant, chances are you are already monitoring everything you put into your body, making sure it's not putting your unborn child at risk.
But a new study contradicts those beliefs. The research, published Monday in the journal JAMA Pediatrics, reports that the children of women who took the drug during pregnancy were about 40% more likely to be diagnosed with attention deficit hyperactivity disorder than children of mothers who took none.
According to the study, the probability of a child developing ADHD symptoms severe enough to require medication increased the most — by 63% — when his or her mother took acetaminophen during the last two trimesters of pregnancy, researchers found. It also rose by about 28% when acetaminophen was used in the third trimester alone. The added risk was smallest — about 9% — when a pregnant woman reported taking the drug only during her first trimester of pregnancy.
The findings do not establish that prenatal exposure to acetaminophen caused the observed increase in diagnosed hyperactivity disorders, prescriptions for ADHD medications, or emotional problems in children reported by parents.
But the research was reportedly designed to avoid many of the pitfalls of studies that find an association between an environmental exposure and the appearance of a specific outcome many years later.
The new findings are based on more than 64,000 Danish mothers and their children. Researchers gathered details on pregnant subjects’ acetaminophen use long before problems in their children’s learning or behavior would have become evident, allowing the study authors to avoid a problem called “recall bias.”
Researchers tracked the study’s pediatric subjects from their first trimester in utero for as long as 15 years. Besides surveying parents about their children’s strengths and weaknesses, the study’s authors used comprehensive and reliable databases — Denmark’s registries of physician diagnoses and of dispensed pharmacy prescriptions — to glean an accurate measure of ADHD in the population.
An editorial published alongside the study praised its “notable methodological strengths,” but cautioned that physicians and pregnant women would be wrong to change their practices based on its findings.
Acetaminophen is an effective fever reducer, and allowing fever and infection to rage unchecked in a pregnant woman can be dangerous for the baby, wrote a trio of British experts on ADHD.
Miriam Cooper of the University of Cardiff in Wales was the lead investigator. Cooper and her team noted that without more details on how acetaminophen might lay the foundations for later ADHD, and when and in whom it is most likely to boost risk, the current findings “should be interpreted cautiously and should not change practice.”