Taking Acetaminophen During Pregnancy Doesn't Cause Neurodevelopmental Disorders, Study Says

Using Tylenol and other brands of Acetaminophen during pregnancy doesn’t increase the baby’s risk of developing neurodevelopmental disorders, new research has found.

While previous studies have suggested that acetaminophen use during pregnancy may increase the risk of neurodevelopmental disorders in children, a large new study refutes this notion — finding that the drug is not actually linked to a higher risk of autism, attention-deficit/hyperactivity disorder (ADHD), or intellectual disability.

The large study, published in JAMA Network Tuesday, is based on a population-based sample of nearly 2.5 million children born between 1995 and 2019 in Sweden, with follow-up through December 31, 2021.

Researchers initially compared children exposed to acetaminophen during pregnancy with those who weren’t and identified marginally increased risks of autism, ADHD, and intellectual disability.

But when conducting an analysis of pairs of siblings with the same biological parents who grew up in the same home — allowing the researchers to account for unobserved genetic and environmental confounders shared between siblings — they found no increased risk of neurodevelopmental disorders from acetaminophen use.

Confounders are factors that influence both variables in a situation and create a false association between them. Without sibling analysis, these confounders can distort study results, which may explain the associations observed in previous research, the authors said.

“Pregnant individuals’ genetics are likely candidates as unmeasured confounders because certain genotypes or phenotypes increase both the probability of acetaminophen use and neurodevelopmental disorders,” the authors wrote.

For example, parents who themselves suffered from autism, ADHD, and intellectual disabilities were found to be more likely to experience pain and more likely to take acetaminophen as a result. This makes it seem as though acetaminophen increases the risk of developing neurodevelopmental disorders when in reality, it is more likely that the disorder was passed down through genetics.

The study found that acetaminophen exposure was more common among children born to parents with a lower socioeconomic position, a higher early pregnancy body mass index, those who smoked during pregnancy, and those with diagnoses of any psychiatric conditions, neurodevelopmental disorders, indications for acetaminophen, and co-prescription of related therapeutics.

“Results suggested that there was not one single ‘smoking gun’ confounder, but rather that multiple birthing parents’ health and sociodemographic characteristics each explained at least part of the apparent association,” the authors wrote.

The study results are significant because, although the US Food and Drug Administration (FDA) and the European Medicines Agency consider acetaminophen to pose minimal risk during pregnancy, a 2021 consensus statement by an international group of scientists and clinicians recommended that pregnant individuals “forego [acetaminophen] unless its use is medically indicated,” among other precautionary actions, due to potential risk of developmental disorders such as autism and attention-deficit/hyperactivity disorder (ADHD).

However, acetaminophen is commonly used to manage pain and fever during pregnancy, and these results suggest that individuals may be able to keep using the drug when needed without worry.

Notably, the study also found no association between neurodevelopmental disorders and using non-aspirin NSAIDs, opioids, and anti-migraine medications in pregnancy after the sibling analysis. Aspirin, meanwhile, was actually found to reduce the risk of neurodevelopmental disorders in the sibling analysis. Still, aspirin is not currently recommended for regular use during pregnancy.

“Acetaminophen use during pregnancy was not associated with children’s risk of autism, ADHD, or intellectual disability in sibling control analyses,” the authors concluded. “This suggests that associations observed in models without sibling control may have been attributable to confounding.”