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Sierra Wells, PharmD
Sierra holds a Bachelor of Science degree with a specialization in drug development and human toxicology and recently completed her Doctor of Pharmacy (PharmD). She now practices as a clinical pediatric pharmacist, where she combines her scientific background with her passion for helping patients and families gain a clear understanding of their medications and treatment plans.
Oct 6, 2025

Neurological Disorder

autism

Does Tylenol Use During Pregnancy Really Cause Autism?

  • Some studies have found a link between acetaminophen (Tylenol) use during pregnancy and autism or ADHD in children, but none prove it causes them.
  • The strongest studies only show associations, and many have limitations like small sample sizes, inconsistent data, and reliance on self-reported information.
  • Key confounding factors, like fever or illness during pregnancy, weren’t always considered, even though they could also affect brain development.
  • Experts agree that current evidence isn’t strong enough to recommend avoiding Tylenol during pregnancy, but more high-quality research is needed.


The current discussion and "hype" surrounding the link between acetaminophen (Tylenol or Paracetamol) use during pregnancy and the development of autism stems from ongoing research into autism.

Autism is a complex condition with no single known cause. Researchers have long studied both genetic and environmental factors that may contribute to its development.

Because brain development begins early in pregnancy, scientists have turned their attention to what happens in the womb, including medications taken by expectant mothers. Acetaminophen has come under scrutiny due to its frequent use and its potential impact on fetal brain development.

But not all research is created equal. While some studies have found associations between acetaminophen use and autism or ADHD, these findings have sparked debate among scientists, healthcare professionals, and the public.

The question remains: Is there truly a cause-and-effect relationship, or are these studies being misinterpreted or overstated?

What We Will Explore

We will take a closer look at the studies that have fueled the hype, including:

  • The three most frequently cited studies linking acetaminophen use during pregnancy to autism and ADHD
  • The limitations and strengths of these studies
  • Whether the evidence supports a causal relationship or merely an association
  • The importance of critical thinking when interpreting scientific research

By examining the validity and the quality of the research, we aim to provide a balanced perspective on a topic that affects millions of families.

Study 1: Measuring Tylenol in Umbilical Cord Blood

Association of Cord Plasma Biomarkers of In Utero Acetaminophen Exposure With Risk of Attention-Deficit/Hyperactivity Disorder and Autism Spectrum Disorder in Childhood (Ji et al., 2020).


What they did Researchers checked the umbilical cord blood of newborns for levels of Tylenol (acetaminophen) and its byproducts.
What they found The study found a link between higher Tylenol levels in the cord blood and a greater risk of a child later being diagnosed with autism or ADHD.
Limitations
  • Small Sample Size: This study looked at a relatively small group of 996 mother-infant pairs. Findings from small studies are often difficult to apply to the entire population.
  • Wrong Timeframe: Tylenol was measured at birth, which mainly reflects use right before or during delivery. However, the brain changes associated with autism happen much earlier in pregnancy (in the first or second trimester). This timing mismatch makes the link unlikely.

Study 2: Combining Data from Multiple European Cohorts

Prenatal and postnatal exposure to acetaminophen in relation to autism spectrum and attention-deficit and hyperactivity symptoms in childhood: Meta-analysis in six European population-based cohorts (Alemany et al., 2021).


What they did This study combined data from six large groups, involving 73,881 mother-child pairs across Europe. Parents reported how often they used acetaminophen during pregnancy, and researchers looked at autism/ADHD symptoms in children aged 4–12.
What they found They found that children whose mothers used Tylenol during pregnancy were 19% more likely to have autism symptoms and 21% more likely to have ADHD symptoms compared to non-exposed children.
Limitations
  • Unreliable Data: The study relied on mothers self-reporting (answering questions about) how much and when they took Tylenol. People often forget or misremember this information, which can make the data unreliable.
  • Failure to Control for Sickness: The biggest issue is that the study did not properly account for the reason the mother took Tylenol (e.g., a high fever or infection). We know that the fever or illness itself—not the medication—is a known risk factor for neurodevelopmental issues.
  • Lack of Significance: When looking at the original six studies, the results were not statistically significant in the majority of them (5 out of 6), meaning the evidence wasn't strong enough to confirm an effect.

Study 3: Systematic Review Using "Navigation Guide" Methodology

Evaluation of the evidence on acetaminophen use and neurodevelopmental disorders using the Navigation Guide methodology. Environ Health 24, 56.


What they did This was a systematic review, which is a high-level summary that pools results from many different smaller observational studies to look for a pattern.
What they found It concluded there was an association (a link), but again, not a cause between Tylenol use and the development of autism/ADHD.
Limitations
  • Observation Only: Observational studies are good for spotting a trend, but they cannot prove cause-and-effect. They simply cannot isolate Tylenol as the sole problem.
  • Confounding Sickness: Like the other studies, the studies included in this review were not consistent in controlling for the fact that the mother may have taken Tylenol because of a fever or serious infection, which could be the true cause of the developmental issues.
  • Inconsistent Data: Some studies used medical records, others relied on parent surveys, making the overall combined data less trustworthy.

The Bottom Line: What Does the Research Really Say?

There’s been a lot of concern lately about whether taking Tylenol (acetaminophen) during pregnancy could increase the risk of autism or ADHD in children. While some studies have found a possible link, it’s important to understand what that really means; and what it doesn’t.

Three major studies have looked into this question. They found associations, not proof of cause. That means they noticed patterns, but they couldn’t say for sure that acetaminophen was the reason for those outcomes.

Each study had important limitations:

  • The largest study looked at fewer than 1,000 children and measured acetaminophen levels at birth, after the critical stages of brain development.
  • A meta-analysis combined results from six European studies (73,881 pairs), but relied on parents’ memories of medication use and questionnaires instead of medical diagnoses.
  • A systematic review concluded that the relationship between acetaminophen and autism was an association at best, not direct causation. Also, most didn’t account for why acetaminophen was taken—like fever or infection, which themselves could affect a baby’s development.

So far, the evidence is not strong enough to say that acetaminophen causes autism or ADHD. Experts agree that more high-quality research is needed. And because it wouldn’t be ethical to test medications on pregnant people in a controlled way, future studies will need to be very carefully designed to account for all the other possible factors.

If you're pregnant and have concerns about taking Tylenol, talk to your healthcare provider. Fever and pain during pregnancy can also pose risks, so it’s important to weigh the benefits and risks together with a professional.

References:

  1. Causes of autism spectrum disorder (ASD). (2020). Public Health Agency of Canada. Retrieved Oct 2, 2025, from https://www.canada.ca
  2. Ji, Y., Azuine, R. E., Zhang, Y., Hou, W., Hong, X., Wang, G., Riley, A., Pearson, C., Zuckerman, B., & Wang, X. (2020). Association of Cord Plasma Biomarkers of In Utero Acetaminophen Exposure With Risk of Attention-Deficit/Hyperactivity Disorder and Autism Spectrum Disorder in Childhood. JAMA psychiatry, 77(2), 180–189. https://doi.org/10.1001/jamapsychiatry.2019.3259
  3. Courchesne, E., Gazestani, V. H., & Lewis, N. E. (2020). Prenatal Origins of ASD: The When, What, and How of ASD Development. Trends in neurosciences, 43(5), 326–342. https://doi.org/10.1016/j.tins.2020.03.005
  4. Alemany, S., Avella-García, C., Liew, Z., García-Esteban, R., Inoue, K., Cadman, T., López-Vicente, M., González, L., Riaño Galán, I., Andiarena, A., Casas, M., Margetaki, K., Strandberg-Larsen, K., Lawlor, D. A., El Marroun, H., Tiemeier, H., Iñiguez, C., Tardón, A., Santa-Marina, L., Júlvez, J., … Sunyer, J. (2021). Prenatal and postnatal exposure to acetaminophen in relation to autism spectrum and attention-deficit and hyperactivity symptoms in childhood: Meta-analysis in six European population-based cohorts. European journal of epidemiology, 36(10), 993–1004. https://doi.org/10.1007/s10654-021-00754-4
  5. Prada, D., Ritz, B., Bauer, A.Z. et al. Evaluation of the evidence on acetaminophen use and neurodevelopmental disorders using the Navigation Guide methodology. (2025). Environ Health 24, 56. https://doi.org/10.1186/s12940-025-01208-0

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