Study author Zeyan Liew of the University of California, Los Angeles, and colleagues studied 64,322 children and mothers in the Danish National Birth Cohort from 1996 to 2002.
Parents reported behavioral problems on a questionnaire, and ADHD medication prescriptions and those for hyperkinetic disorders -- a severe form of ADHD -- were collected from Danish registries.
More than half of the mothers reported using acetaminophen while pregnant. The use of acetaminophen during pregnancy appeared to be associated with a higher risk of HKD diagnosis, of using ADHD medications or of having ADHD-like behaviors at age 7.
The risk increased when mothers used acetaminophen in more than one trimester during pregnancy, Liew said.
"Maternal acetaminophen use during pregnancy is associated with a higher risk for HKDs and ADHD-like behaviors in children," Liew and colleagues wrote in the study. "Because the exposure and outcomes are frequent, these results are of public health relevance but further investigations are needed."
The findings were published in the journal of the American Medical Association Pediatrics.