Acetaminophen in Pregnancy and Autism Risks: A Review of the Research
Introduction
A renewed debate has emerged in the United States over whether prenatal use of acetaminophen (commonly known as Tylenol or paracetamol) may be linked to autism spectrum disorder (ASD). President Donald Trump and Health and Human Services Secretary Robert F. Kennedy Jr. have called for further research into the matter and announced steps including new warning labels, physician alerts, and expanded studies.
Their remarks have drawn widespread attention, as acetaminophen is one of the most widely used medications during pregnancy. Health organizations and researchers emphasize that while some studies have found associations between acetaminophen use in pregnancy and later developmental outcomes, current scientific evidence does not establish a causal relationship.
What the Research Shows
Acetaminophen has been used for pain and fever relief since the 1950s and is generally considered the first-choice painkiller during pregnancy. Research over the past decade has produced mixed results:
- Associations Reported: An August 2025 meta-analysis by researchers at Mt. Sinai, Harvard, UCLA, and UMass Lowell reviewed 46 studies. It found an association between prenatal acetaminophen exposure and later diagnoses of autism and ADHD. However, the authors cautioned that their findings did not prove causation and recommended against discontinuing the drug without physician guidance.
- Sibling Comparison Studies: A Swedish study analyzing health records of 2.4 million children (1995–2019) found that 1.42% of children exposed to acetaminophen during pregnancy were autistic compared to 1.33% of children not exposed, a small difference. When comparing siblings, the association disappeared, suggesting other genetic or environmental factors were responsible.
- Japanese Research: A 2025 study of over 200,000 children in Japan reached similar conclusions, finding no significant causal link once genetic and family-related factors were considered.
- Other Reviews: Some systematic reviews have suggested possible associations, while others concluded that acetaminophen is unlikely to pose a clinically important risk for autism spectrum disorder.
In short, while some observational studies raise questions, high-quality controlled research generally does not support acetaminophen as a cause of autism.
Why Associations May Appear
Experts highlight that confounding factors complicate research in this area. For example:
- Mothers who take acetaminophen during pregnancy may do so because of fever or underlying conditions, which themselves can be linked with developmental outcomes.
- Genetic influences on both immune response and pain perception may overlap with autism risk factors, making it appear that acetaminophen is linked when it is not.
This makes it difficult to separate correlation from causation in population studies.
Autism Rates and Contributing Factors
Autism prevalence has risen significantly over recent decades:
- A 2025 CDC report estimated that 1 in 31 eight-year-olds in the U.S. had an ASD diagnosis in 2022, compared with 1 in 36 in recent years and much lower rates in the 1980s.
- Experts attribute much of this increase to greater awareness, broader diagnostic criteria, and improved screening, rather than a single environmental factor.
- Genetics play a major role in autism, though researchers continue to study how parental age, prenatal health, and environmental influences may contribute.
The Leucovorin Question
The U.S. government also announced steps to accelerate the approval process for leucovorin, a folate-based drug traditionally used in cancer treatment. Small studies suggest it may benefit a subset of autistic children with cerebral folate deficiency. While promising, experts note that more controlled trials are needed before leucovorin can be recommended as a standard autism treatment.
Current Guidance for Pregnant Women
Health authorities including the American College of Obstetricians and Gynecologists (ACOG), the American Academy of Pediatrics (AAP), and the U.S. Food and Drug Administration (FDA) continue to state that acetaminophen remains safe for use in pregnancy when taken as directed.
- Benefits: Acetaminophen is the only widely approved option for treating fever in pregnancy, and untreated high fever can increase risks such as neural tube defects and preterm birth.
- Risks: No causal link has been proven between acetaminophen and autism. Some associations have been reported, but they are small and inconsistent.
Pregnant women are advised to consult their physicians before making decisions on medication use.
Conclusion
The question of whether acetaminophen use in pregnancy contributes to autism remains under scientific investigation. While some studies have reported associations, large-scale and sibling-controlled research does not support a causal relationship. Autism is a complex condition influenced by genetic and environmental factors, and no single exposure has been identified as a primary cause.
As research continues, health experts emphasize the importance of balancing caution with the proven benefits of acetaminophen in pregnancy. At present, medical consensus holds that the medication remains safe when used clinically, and ongoing studies will help clarify any potential risks.
