A new study from researchers at the Johns Hopkins Bloomberg School of Public Health has found that exposure to acetaminophen in the womb may increase a child's risk for attention deficit hyperactivity disorder or autism spectrum disorder.
The researchers analyzed data from the Boston Birth Cohort, a 20-year study of early life factors influencing pregnancy and child development. They found that children whose cord blood samples contained the highest levels of acetaminophen—the generic name for the drug Tylenol—were roughly three times more likely to be diagnosed with ADHD or autism spectrum disorder later in childhood, compared to children with the lowest levels of acetaminophen in their cord blood.
Their findings were published last week in JAMA Psychiatry.
Previous studies have found an association between maternal use of acetaminophen during pregnancy and increased risks of adverse childhood outcomes, including neurodevelopmental disorders such as ADHD—which is marked by hyperactivity and difficulty paying attention or controlling impulsive behavior—and autism spectrum disorder, a complex developmental disorder that can affect how a person socializes, communicates, and behaves. Because these studies relied on mothers self-reporting their acetaminophen use, critics have said the findings may be affected by recall bias or lack an objective measure of in-utero exposure. As a result, the U.S. Food and Drug Administration has refrained from making recommendations regarding the use of acetaminophen during pregnancy.
"People in general believe Tylenol is benign, and it can be used safely for headaches, fever, aches, and pains," says Xiaobin Wang, a professor in the Bloomberg School's Department of Population, Family, and Reproductive Health and the study's corresponding author. "Our study further supports the concerns raised by previous studies—that there is a link between Tylenol use during pregnancy and increased risk for autism or ADHD."
For the study, which was authored by Johns Hopkins postdoctoral fellow Yuelong Ji and colleagues, the team measured the biomarkers of acetaminophen and two of its metabolic byproducts in umbilical cord blood samples from 996 individual births. Every sample analyzed contained some level of acetaminophen—confirming the drug's widespread use during pregnancy, labor, and delivery. The researchers then divided the study children into three groups based on the amount of acetaminophen and its metabolites present in their cord blood samples.
Compared to the group with the lowest amount of acetaminophen exposure, the children in the middle third group were about 2.26 times more likely to have an ADHD diagnosis and 2.14 times more likely to have an autism spectrum disorder diagnosis. Those with the highest levels of exposure were associated with 2.86 times the risk of ADHD and 3.62 times the risk for autism spectrum disorder, compared to those with the lowest exposure.
The researchers found consistent associations between the drug and the disorders across a variety of other factors that correlate with ADHD and autism spectrum disorder diagnoses, such as maternal BMI, preterm birth, child sex, and reports of maternal stressors and substance use.
Wang points out that although the study found a consistent association between biomarkers of acetaminophen and its metabolites in cord blood and child risk of ADHD and autism spectrum disorder, it should not be interpreted that the Tylenol use causes these disorders.
"More studies are clearly needed to further clarify the concern," Wang says. "Until it is certain, parents and providers may want to consider the benefit and potential risk when making a decision on the use of acetaminophen during pregnancy or the peripartum period."