Study Questions Safety of Acetaminophen Use in Pregnancy

Children born to women who take acetaminophen during pregnancy may be at increased risk for attention deficit hyperactivity disorder (ADHD) and similar behavioral problems, a new study suggests.

The study, published in JAMA Pediatrics, does not establish causality, the authors point out in suggesting the study should be replicated. The findings, however, raise the question about if the common painkiller should continue to be considered safe for use by pregnant women. 

Pertinent Points

- Children born to women who take acetaminophen during pregnancy may be at increased risk for attention deficit hyperactivity disorder (ADHD) and similar behavioral problems.

- Children born to these women were 37% more likely to have hyperkinetic disorder, 29% more likely to be prescribed ADHD medications, and 13% more likely to exhibit ADHD-like behaviors at age 7.

- Additional study is needed to determine causality.

Researchers at UCLA, in collaboration with the University of Aarhus in Denmark, evaluated 64,322 children and mothers enrolled in the Danish National Birth Cohort during 1996-2002. Of those, 56% of mothers reported using acetaminophen while pregnant.

Children born to these women were 37% more likely to receive a diagnosis of hyperkinetic disorder (hazard ratio = 1.37; 95% CI, 1.19-1.59). The prenatally exposed children were also 29% more likely to be prescribed ADHD medications (hazard ratio, 1.29; 95% CI, 1.15-1.44) and 13% more likely to exhibit ADHD-like behaviors at age 7 (risk ratio, 1.13; 95% CI, 1.01-1.27).

Stronger associations were observed when mothers used the drug in more than one trimester during pregnancy. In addition, greater exposure to acetaminophen increased the link for all three outcomes.

"The causes of ADHD and hyperkinetic disorder are not well understood, but both environmental and genetic factors clearly contribute," said Beate Ritz, MD, PhD, professor and chair of the department of epidemiology at the UCLA Fielding School of Public Health and one of the study authors. "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."

Acetaminophen can cross the placental barrier, Ritz explained, suggesting it is possible that the drug could interrupt fetal brain development.

An editorial accompanying the study noted the study had several methodological strengths, including an adjustment for things that might have also influenced fetal development, such as inflammation or fever in the mother. Still, since the researchers could not account for every reason the women took acetaminophen, the editorial agreed that more study is needed.

References:

Liew Z, Ritz B, Rebordosa C, et al. Acetaminophen use during pregnancy, behavioral problems, and hyperkinetic disorders. JAMA Pediatr. February 24, 2014. doi:10.1001/jamapediatrics.2013.4914.