By Pat Anson, PNN Editor 

A large new study in Europe is adding to the growing body of evidence that the use acetaminophen (paracetamol) by pregnant women raises the risk of their children having autism or Attention-Deficit Hyperactivity Disorder (ADHD)

Researchers at the University of Barcelona followed nearly 74,000 mothers and their children in the UK and five other European countries, finding that women who took the pain reliever while pregnant were 19% more likely to have children with Autism Spectrum Conditions (ASC) and 21% more likely to develop ADHD symptoms.

“Associations between prenatal acetaminophen and ASC and ADHD symptoms were consistently positive for both boys and girls albeit slightly stronger among boys,” researchers reported in the European Journal of Epidemiology.

Several previous studies have linked prenatal use of acetaminophen to autism, ADHD and hyperactivity in children, but this was by far the largest. Although the exact cause is unknown, it’s believed acetaminophen affects a baby’s brain development and growth, especially during the third trimester. The study found no evidence that acetaminophen raised the risk of autism and ADHD after the children were born.

Despite the findings, the UK’s National Health Service (NHS) maintains that it is safe for pregnant women to use paracetamol.

“Paracetamol is the first choice of painkiller if you're pregnant or breastfeeding. It's been taken by many pregnant and breastfeeding women with no harmful effects in the mother or baby,” the NHS says on its website.

The U.S. Food and Drug Administration also does not caution pregnant women about using acetaminophen. The agency said in 2015 that the evidence was “too limited” to justify such a warning.  

The University of Barcelona researchers are a bit more cautious, saying pregnant women should take acetaminophen “only when necessary.”

“Considering all evidences on acetaminophen use and neurodevelopment, we agree with previous recommendations indicating that while acetaminophen should not be suppressed in pregnant women or children, it should be used only when necessary,” they said.

Acetaminophen is the most popular pain reliever in the world, and is used by over half the pregnant women in Europe and the United States. It is the active ingredient in Tylenol, Excedrin, and hundreds of pain medications. Excessive use of acetaminophen can cause liver, kidney, heart and blood pressure problems. A recent study found little or no evidence to support its use for most pain conditions.