Questions about whether acetaminophen use during pregnancy can lead children to develop neurological problems have sparked scientific inquiry and litigation. Lawsuits are continuing, but a new National Institutes of Health-sponsored study has results that show no causal link between acetaminophen and neurodevelopmental disorders.

By Frank Vinluan

When women experience pain or fever during pregnancy, many clinicians recommend acetaminophen for relief. But concerns about a possible link between these medicines and neurodevelopmental disorders have lingered. A multi-year study sponsored by the National Institutes of Health has results that add to the scientific consensus that these medicines aren’t the cause of neurodevelopmental problems.
Acetaminophen is the active pharmaceutical ingredient in some prescription products and popular over-the-counter pain relievers, notably Tylenol and Excedrin. While nonsteroidal anti-inflammatory drugs offer an alternative approach to pain relief, these drugs aren’t recommended during pregnancy because they can cause low levels of amniotic fluid among other problems.
The NIH-sponsored acetaminophen study was a collaboration between Swedish and U.S. investigators. They evaluated data from Swedish birth and prescription drug records for children born between 1995 and 2019. Follow-up follow was done through Dec. 31, 2021. Of the more than 2.4 million Swedish children whose data were reviewed, 185,909 (7.49%) were exposed to acetaminophen during pregnancy. Results showed a slight increase in the probability of developing autism, attention-deficit/hyperactivity disorder (ADHD), or intellectual disability in those who were exposed to acetaminophen compared to those who were not.
To address questions about whether some other factors might be at play, scientists also analyzed children matched with a sibling as a control. Sibling controls enabled scientists to compare subjects who share many variables, such as genetics, environmental exposures, and socioeconomic factors.
“Sibling control analyses found no evidence that acetaminophen use during pregnancy was associated with autism or intellectual disability,” the study authors wrote.
The American College of Obstetricians and Gynecologists recommends acetaminophen (also known as paracetamol) for pain relief during pregnancy. The organization’s position is that the drug is one of the few pain relievers safe to use while pregnant and there is no clear evidence proving a direct relationship between acetaminophen and fetal development issues. Lawsuits alleging a link have mounted, but they haven’t made their claims stick. Late last year, a federal judge ruled that the plaintiffs in a consolidated mass tort of nearly 500 cases failed to show scientific evidence that prenatal exposure to acetaminophen can lead to autism or ADHD.
There are limitations to the NIH study. It relies on data from prescribed acetaminophen and from pregnant individuals self-reporting during prenatal care, the NIH said. Consequently, the study may not capture all acetaminophen use or dosage in all people. However, the size of the study sample and the ability to control for many other confounding factors support the conclusion that acetaminophen is not directly linked to an increase link of autism, ADHD, or intellectual disability, the NIH said. To fully understand the genetic and non-genetic factors that increase those risks, more research is needed.
The study was funded by the National Institute of Neurological Disorders and Stroke, a part of the NIH. The results were published earlier this month in the journal JAMA.
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