Acetaminophen (paracetamol) is the most commonly used medication for pain and fever during pregnancy.
Some recent studies have suggested that acetaminophen has effects on sex and other hormones, which can in turn affect neurodevelopment and cause behavioural dysfunction.
Zeyan Liew, of the University of California, Los Angeles, and colleagues studied 64,322 children and mothers in the Danish National Birth Cohort (1996-2002).
Parents reported behavioural problems on a questionnaire. Researchers collected attention-deficit/hyperactivity disorder (ADHD) medication prescriptions and hyperkinetic disorders (HKDs) diagnoses from Danish registries.
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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 behaviours at age 7 years.
The risk increased when mothers used acetaminophen in more than one trimester during pregnancy.
"Maternal acetaminophen use during pregnancy is associated with a higher risk for HKDs and ADHD-like behaviours in children. Because the exposure and outcomes are frequent, these results are of public health relevance but further investigations are needed," researchers said.
The study was published in the Journal of the American Medical Association (JAMA) Pediatrics.