For years, acetaminophen has been considered a safe medication for pregnant women for use as a pain reliever and/or fever reducer. However, a new study is casting a shadow over use of the drug during pregnancy.

A study conducted by a team of researchers from the Cardiff University School of Medicine shows an association between acetaminophen use by pregnant women and a later diagnosis of ADHD and other hyperkinetic disorders in their children.

Although ADHD can be inherited, the authors assert that lead and other toxins have been causally linked to the disorder — however, the acetaminophen/ADHD link has not been deemed causal at this point. More study is needed to understand the true relationship between the two. Indeed, there are other factors to consider, such as how the drug is metabolized in individual women, and what the residual affects are.

For the study, the team gathered data from the Danish National Birth Cohort; because acetaminophen is considered safe, 56% of the women who participated in the study had been exposed to acetaminophen at some point. The researchers determined that the association was there regardless of whether acetaminophen was taken for pain or for a fever.

Children of women who took acetaminophen for more than one trimester were even more likely to be diagnosed with ADHD.

Researchers emphasize that in some cases, the benefits of taking acetaminophen exceeds risk substantially, especially if a pregnant is diagnosed with pre-eclampsia or has other complications that need to be addressed.

According to the ADD Research Council,  the percentage of children diagnosed with ADHD has risen from 7%-9% over the last ten years.

Symptoms of ADHD are inattention, impulsive behavior and hyperactivity. If left untreated, the disorder can lead to function impairment in school, social, and familial settings.

For more information on ADHD, visit the ADD Research Council website.