By Pat Anson, PNN Editor

A new study is adding to the growing body of evidence linking maternal use of acetaminophen to hyperactivity and other behavioral problems in children. Acetaminophen – which is more commonly known as paracetamol outside the U.S. – is the world’s most widely used over-the-counter pain reliever.

British researchers have been following over 14,000 children born in 1991 and 1992 who are enrolled in the Avon Longitudinal Study of Parents and Children. The children’s health, cognitive skills, temperament and behavior were regularly evaluated as they grew older.

Children with mothers who regularly used acetaminophen in mid to late pregnancy were more likely to be hyperactive, less adaptable and to have conduct problems in their pre-school years. The attention and hyperactivity issues appear to lessen by age 7, although boys exposed to the drug were more likely to have conduct problems until age 9.

“We have shown that paracetamol consumption between 18 and 32 weeks gestation was associated with adverse trends in pre‐school child behaviour, but the associations were no longer present by the end of primary school (age 10‐11 years). Boys appeared to be more susceptible than girls to possible behavioural effects of the drug,” researchers reported in the journal Paediatric and Perinatal Health.

Acetaminophen is used by over half the pregnant women in the United States and European Union. It is the active ingredient in Tylenol, Excedrin, and hundreds of pain medications.

Previous studies have linked maternal use of acetaminophen to asthma, autism and attention deficit disorder (ADHD) in children, as well as early puberty and slow language development in girls.

“Our findings add to a series of results concerning evidence of the possible adverse effects of taking paracetamol during pregnancy such as issues with asthma or behaviour in the offspring,” said lead author Professor Jean Golding of the University of Bristol.

“It reinforces the advice that women should be cautious when taking medication during pregnancy and to seek medical advice where necessary.”

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

“Paracetamol has been used routinely during all stages of pregnancy to reduce a high temperature and for pain relief. There's no clear evidence it has any harmful effects on an unborn baby,” the NHS says on its website.

The FDA’s warning label for acetaminophen cautions people about the risk of liver damage and other side effects, but does not specifically warn pregnant women about using the pain reliever. The agency said in 2015 that the evidence was “too limited” to justify such a warning.