A new study from the University of Washington suggests that using acetaminophen (also known as paracetamol) during pregnancy may increase the risk of children developing attention deficit hyperactivity disorder (ADHD).
The research focused on a group of 307 African American mother-child pairs. Scientists analyzed blood samples from pregnant mothers during their second trimester to detect acetaminophen. They then checked whether these children were diagnosed with ADHD by the ages of 8 to 10.
The results showed that children whose mothers had acetaminophen in their blood during pregnancy were more than three times as likely to develop ADHD compared to those without exposure.
Acetaminophen and Pregnancy
Acetaminophen is a common pain reliever and fever reducer. It is widely used during pregnancy, with studies showing that 41–70% of pregnant individuals in the U.S., Europe, and Asia take it. Health authorities, such as the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA), consider acetaminophen to be a low-risk medication.
However, growing research suggests it might have long-term effects on a baby’s brain development. Some studies have linked prenatal acetaminophen use to conditions such as ADHD and autism spectrum disorder.
Many previous studies relied on self-reports from pregnant women about whether they took acetaminophen, which could lead to errors or biases in the data. The new study improves on this by directly measuring acetaminophen levels in maternal blood, making the results more reliable.
How the Study Was Conducted
The study was part of the Conditions Affecting Neurocognitive Development and Learning in Early Childhood (CANDLE) project, which follows children from birth to examine factors affecting brain development. The research team used a method called metabolomics to detect acetaminophen and its byproducts in the mothers’ blood samples.
They found acetaminophen in 20.2% of the mothers’ blood samples. Children whose mothers had these markers in their blood were 3.15 times more likely to be diagnosed with ADHD.
Interestingly, the risk was much higher in female children—those exposed to acetaminophen in the womb had a 6.16 times greater chance of developing ADHD. In male children, the link was weaker and not statistically significant.
How Acetaminophen Might Affect Brain Development
To understand why acetaminophen exposure in the womb could increase ADHD risk, the researchers also studied placental gene activity. In a smaller group of 174 participants, they found that exposure to acetaminophen affected the placenta differently based on the baby’s sex.
- In females, acetaminophen exposure increased the activity of genes related to the immune system, including a gene called IGHG1, which was linked to ADHD.
- In both males and females, acetaminophen exposure reduced the activity of genes involved in energy production in cells. Similar changes have been linked to brain development problems in other studies.
What This Means
These findings add to previous research suggesting a link between prenatal acetaminophen use and ADHD. By using direct blood measurements instead of self-reported medication use, this study strengthens the evidence for a connection.
However, more research is needed to understand why acetaminophen affects brain development in this way and why it seems to impact female children more than males. Scientists also want to explore whether other medications or environmental factors could play a role in these effects.
For now, experts suggest that pregnant individuals use acetaminophen only when necessary and talk to their doctors about any concerns.
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The research findings can be found in Nature Mental Health.
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