Tylenol and Pregnancy: Harvard Study discusses Acetaminophen, Autism and ADHD Risks

Friday, August 22, 2025.

For decades, acetaminophen—paracetamol to much of the world, Tylenol if you’re in a U.S. pharmacy aisle—has been the quiet, trusted companion of pregnant women.

A fever? Take two. A pounding headache? Same advice. Back pain in month seven? Doctors have nodded yes for years.

It’s not hard to see why. Nearly half of pregnant women in the UK and about two-thirds in the U.S. take it at some point. For decades, it was waved through as the “safest option.”

But now, researchers from Harvard and Mount Sinai are urging caution.

After reviewing more than 100,000 cases, their conclusion is sobering: prenatal acetaminophen use may be linked to higher risks of autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD).

Not proof. Not a verdict. But the strongest evidence so far that this everyday drug perhaps isn’t as risk-free as we once believed.

What the Study Found

The researchers pulled together 46 separate studies, tracking when acetaminophen was taken during pregnancy—first trimester, second, third, or throughout—and linking it to children’s later diagnoses.

Their review, published in Environmental Health, claimed:

• Emerging evidence connecting prenatal acetaminophen use and ADHD.

• Emerging evidence connecting prenatal use and autism.

• Higher-quality studies were most likely to show the link.

As Dr. Diddier Prada of Mount Sinai explained, “the stronger the study design, the stronger the association looked.”

Why This Matters

Acetaminophen is still safer than many alternatives. Ibuprofen and aspirin, for example, can cause real complications late in pregnancy. And untreated fever can itself harm a fetus.

But here’s the uneasy truth: when a drug is taken by millions, even a small increase in risk becomes a public health issue.

There is absolutely no causal association. That’s why the current advice is not to panic, not to stop cold turkey—but to perhaps use it more sparingly. Lowest dose. Shortest time. But always talk to your doctor.

Autism and ADHD Are Rising

The conversation lands at a moment when autism and ADHD diagnoses are already surging.

• Autism: In 2000, about 1 in 150 U.S. children were diagnosed. By 2020, it was 1 in 31. Some of this rise is due to better screening, but a 2024 study of 12.2 million health records found a 175% increase in diagnoses over 11 years (Zhou et al., 2024).

• ADHD: In England, for example, prescriptions for ADHD medications now exceed 230,000 people, rising by 20% in a single year—the steepest jump on record. Adult women, not just children, are now driving this increase.

Meanwhile, almost 130,000 British children are stuck waiting for autism assessments, a backlog one commissioner called an “invisible crisis.”

The Counterargument: Not Everyone’s Convinced

This isn’t an open-and-shut case.

• Some studies suggest that maternal fever, not the acetaminophen itself, could be the culprit.

• Others note that much of the data relies on mothers recalling what they took, introducing recall bias (Duan et al., 2021).

• And since randomized controlled trials would be unethical, we’re left with observational studies. They’re strong at showing patterns, but weaker at proving cause and effect. This is a very essential point. It is a wild overstatement to claim that Tylenol causes autism.

That leaves us in a gray zone: acetaminophen could be part of the story, or simply one clue in a larger puzzle of genetics, health, and environment.

What Expectant Parents Should Do

• Don’t panic. Acetaminophen remains safer than many alternatives.

• Talk to your provider. Each pregnancy is unique, and professional advice is key.

• Use sparingly. Lowest effective dose, shortest possible time.

• Stay informed. Research is evolving quickly.

The Bigger Picture

Autism and ADHD aren’t diseases to “cure.”

They’re forms of neurodiversity that shape lives in challenging and often meaningful ways.

But if a common painkiller, taken casually, is shifting developmental outcomes at a population level—even a little—that deserves serious attention.

As Dr. Prada warned: “A small risk, multiplied across millions, could have major public health implications.”

Tylenol (acetaminophen) is still the first-line option for pregnant women, but it may not be as harmless as once believed. Use it wisely, use it sparingly, and always involve your doctor in the decision.

Frequently Asked Questions

Does Tylenol cause autism in babies?
No study has ever proven that Tylenol directly causes autism. Researchers have found a strong association between prenatal acetaminophen use and autism, but more studies are needed before any direct causation can be claimed.

Can taking Tylenol while pregnant cause ADHD in children?
Some large, high-quality studies suggest a link between prenatal Tylenol use and ADHD diagnoses. But this does not prove direct causation—it only signals an increased risk worth monitoring.

Is Tylenol safe during pregnancy?
Yes—acetaminophen is still considered the safest painkiller for pregnant women. However, experts recommend using the lowest dose for the shortest time possible.

What pain relievers are safe for pregnancy besides Tylenol?
Acetaminophen is preferred. Ibuprofen and aspirin are generally discouraged, especially in later pregnancy, because of known risks to fetal development.

Is Tylenol safe in the first trimester of pregnancy?
Doctors still consider it safer than alternatives, but the new research suggests caution. Short-term, low-dose use under medical advice is the current best practice.

Should I stop taking Tylenol now that I’m pregnant?
No. Stopping suddenly without medical advice could be more harmful. Fever and severe pain can also endanger the baby. Talk to your doctor before making any changes.

Be Well, Stay Kind, and Godspeed.

REFERENCES:

Duan, L., Ng, A., Chen, W., Spencer, H., et al. (2021). Paracetamol use during pregnancy and neurodevelopment: An updated systematic review and meta-analysis. Pharmacoepidemiology and Drug Safety, 30(6), 823–837. https://doi.org/10.1002/pds.5210

Ji, Y., Azuine, R. E., Zhang, Y., Hou, W., Hong, X., Wang, G., ... & 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

Zhou, H., Yang, L., & Xu, H. (2024). Trends in autism spectrum disorder diagnoses among 12.2 million individuals across 11 years. Journal of Autism and Developmental Disorders. Advance online publication. https://doi.org/10.1007/s10803-024-06511-4

Bauer, A. Z., Kriebel, D., Herbert, M. R., Bornehag, C. G., Swan, S. H., & Zoeller, R. T. (2021). Paracetamol use during pregnancy—a call for precautionary action. Nature Reviews Endocrinology, 17(12), 757–766. https://doi.org/10.1038/s41574-021-00553-7