A two-decade-long, large-scale study from Hong Kong found no evidence of links between taking paracetamol (acetaminophen) during pregnancy and an increased risk of autism spectrum disorder (ASD) or attention-deficit/hyperactivity disorder (ADHD) in children.

The scientists used a statistical method called a sibling-matched design to analyze more than 708,020 mother-child pairs in Hong Kong. By comparing siblings within the same family, where one was exposed to paracetamol in the womb and the other was not, they could better isolate the drug's effect while accounting for shared genetics and home environment that might otherwise bias the findings.

The finding of no link to ASD or ADHD held true regardless of dose or timing. It didn't matter whether mothers took a little or a lot, or whether they took it in the early weeks or the final stretch of pregnancy.

The findings are published in JAMA Internal Medicine.

Familial factors or paracetamol?

Tylenol's, or paracetamol's, safety during pregnancy is back in the spotlight after the U.S. president claimed it increases the risk of autism in children. The concern stems from observational studies reporting a possible association between prenatal paracetamol exposure and conditions such as autism (ASD) and ADHD.