University Study Questions Whether Acetaminophen Is Safe for Pregnant Women

The results of a long-term study conducted by researchers at the University of California at Los Angeles and the University of Aarhus in Denmark show that use of acetaminophen during pregnancy can lead to attention deficit hyperactivity disorder (ADHD) in their children. Acetaminophen, found in over-the-counter drugs such as Tylenol, has been used regularly by pregnant women since the 1950s.

The researchers studied 64,322 children and mothers in Denmark from 1996 to 2002. The researchers surveyed the women during their pregnancies and followed up with parents when their children reached the age of 7. More than half of all the mothers reported using acetaminophen while pregnant. The researchers found that children whose mothers used acetaminophen during pregnancy were at a 13 percent to 37 percent higher risk of later receiving a hospital diagnosis of hyperkinetic disorder, being treated with ADHD medications or having ADHD-like behaviors at age 7. The longer acetaminophen was taken — that is, into the second and third trimesters — the stronger the associations.

“The causes of ADHD and hyperkinetic disorder are not well understood, but both environmental and genetic factors clearly contribute,” said Dr. Beate Ritz, professor and chair of the department of epidemiology at the Fielding School of Public Health at UCLA and one of the senior authors of the paper. “We know there has been a rapid increase in childhood neurodevelopmental disorders, including ADHD, over the past decades, and it’s likely that the rise is not solely attributable to better diagnoses or parental awareness. It’s likely there are environmental components as well.”

The paper, “Acetaminophen Use During Pregnancy, Behavioral Problems, and Hyperkinetic Disorders,” was published on the website of the journal JAMA Pediatrics. It may be accessed here.