An international study carried out by a group of researchers in Norway, the United States and the United Kingdom has found that use of acetaminophen during pregnancy can raise the risk of attention-deficit / hyperactivity disorder (ADHD) in the offspring.

The findings of the study, ‘Prenatal Exposure to Acetaminophen and Risk of ADHD’ were published in the November 2017 edition of the medical journal, Pediatrics.

The study was led by Dr. Eivind Ystrom at the Norwegian Institute of Public Health in Oslo, Norway and carried out  with researchers from the University of Oslo; Columbia University of New York; New York State Psychiatric Institute; University of Bristol in the UK; and the University of Bergen in Bergen, Norway.

The team examined the association between maternal use of acetaminophen during pregnancy, and paternal use of acetaminophen before pregnancy, to estimate its association with ADHD in the offspring. The researchers adjusted for familial risk for ADHD and the indications of acetaminophen use.

Diagnoses were obtained from the Norwegian Patient Registry for 112,973 offspring from the Norwegian Mother and Child Cohort Study, including 2,246 with ADHD. The researchers estimated hazard ratios (HRs) for an ADHD diagnosis by using Cox proportional hazard models.

The researchers reported that they found a “modest association between ‘any prenatal maternal use’ of acetaminophen” in all three trimesters of pregnancy.

The hazard ratio for ‘more than 29 days of maternal acetaminophen use’ was nearly double that figure.

Use for ‘less than eight days’ was not associated with ADHD, according to the researchers.

“Acetaminophen use for fever and infections for 22 to 28 days was associated with ADHD,” the researchers wrote. “Paternal and maternal use of acetaminophen were similarly associated with ADHD.”

The team concluded, “Short-term maternal use of acetaminophen during pregnancy was negatively associated with ADHD in offspring.

“Long-term maternal use of acetaminophen during pregnancy was substantially associated with ADHD even after adjusting for indications of use, familial risk of ADHD, and other potential confounders.”

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