Tylenol (Acetaminophen) in Pregnancy and Autism: What the Studies Show

If you’ve felt whiplash from acetaminophen and autism headlines, you’re not imagining it. The claims are loud, but the louder they get, the more important it is to pause and look closer.

First: it’s important to remember that acetaminophen is the generic name of a medication. Acetaminophen is the ingredient in Tylenol, paracetamol (common international but just goes by a different name), and OTC meds like NyQuil, DayQuil, Theraflu, Mucinex products, Excedrin (which also has caffeine and aspirin), Midol, Alka-Seltzer Plus, and many others often include acetaminophen.

Science doesn’t work in one-liners. Every study has strengths and limitations. Some rely on self-report, which can introduce bias. Others can’t always separate medicine from the reason it was taken, like a fever or infection. Many don’t fully account for family traits and genetics, which play a big role in neurodevelopment. When those factors aren’t included, results can sound more conclusive than they really are. That’s why how we interpret research matters just as much as the results themselves.

The value of research comes when it’s weighed together. Study against study, along with medical expertise, and in the context of a parent’s health. That’s the foundation of evidence-based practice. It’s not about dismissing research or clinging to a single result. It’s about putting the pieces together so they form something useful for real families, in real life.

Why is this coming up now?

Questions about acetaminophen use during pregnancy aren’t new. It’s one of the most commonly used medications in pregnancy, and ACOG has long considered it safe when used as directed. But concerns about possible links to autism or ADHD continue to resurface, and lately, the volume has turned up.

Part of that is timing: autism diagnoses are rising as awareness and evaluation improve, and public debates often look for a single cause to explain it. Add in a recent press conference full of sweeping statements and stigma, and the conversation has landed right back in parents’ laps.

This is where source matters. A headline or sound bite can make a study sound conclusive. The real insight comes from how the research was done, and what its design can and can’t tell us. That’s why it’s worth looking more closely at the most-cited studies.

The Harvard/Mount Sinai review

You may have seen this one referenced a lot: a 2025 review from Harvard and Mount Sinai that pulled together 46 studies on acetaminophen use in pregnancy and developmental outcomes like autism and ADHD. On the surface, it sounds big and definitive, and the authors concluded there was “evidence consistent with an association.”

So what did that look like? Of the studies they included, 27 found some kind of link, 9 didn’t, and 4 even suggested a protective effect. The authors leaned on the studies they considered higher-quality, which more often showed a small increase in risk. Their bottom line: acetaminophen should be used cautiously in pregnancy, only when needed, and at the lowest dose for the shortest time.

That advice isn’t wrong. It’s what most OBs already recommend. And the review itself was rigorous in how it graded each study’s strengths and weaknesses, which is a good thing. Parents deserve transparency about how research is weighed.

But here’s the catch: the studies it combined were all over the map. Most relied on mothers self-reporting acetaminophen use during pregnancy, which is still vulnerable to bias. One study pulled from a prescription database instead. Each measured developmental outcomes in different ways. That kind of variation makes it nearly impossible to pin down a single “effect size” or clear risk.

Confounding also remains a key issue: genetics, family traits, and the specific reasons people take acetaminophen in the first place (like fever, infection, or pain) can all influence child development and may explain some of the associations. And because all the data was observational, it can’t fully rule out these other explanations.

Randomized controlled trials, the kind of study that best establishes cause and effect, will never happen in this situation. It wouldn’t be ethical to ask pregnant people to take or avoid a medication that might cause harm, just as it wouldn’t be ethical to withhold a life-saving vaccine in a clinical trial.

So we rely on observational data here, knowing it has limits.

This review is helpful because it shows how much has been studied, and it encourages cautious use. But it’s not proof of cause and effect. The results were mixed, and the strongest designs didn’t show a link. That’s why one review, even a big one, shouldn’t be the only deciding factor for parents making real-life choices.

The Swedish sibling cohort study

Another study that gets a lot of attention, and for good reason, is a massive analysis from Sweden, published in JAMA in 2024. Researchers looked at nearly 2.5 million children born between 1995 and 2019, using national health and prescription records to track acetaminophen use in pregnancy and later diagnoses of autism, ADHD, or intellectual disability.

At first glance, the results looked similar to other studies: in the general population, there were very small increases in risk. Statistically, those differences showed up, but they were so minor it’s hard to know if they meant anything in real life.

Here’s where this study stands out. The researchers compared siblings within the same family, one pregnancy with acetaminophen use, another without. This kind of design controls for many genetic and environmental factors that families share. When they ran those sibling comparisons, the associations disappeared. The risk of autism, ADHD, or intellectual disability was essentially the same regardless of acetaminophen use. Even when they looked at higher or longer use, there was no dose-response effect.

That’s a major strength. It shows how unmeasured factors, like genetics, maternal health conditions, or the reason the medication was taken in the first place, can create the appearance of risk in simpler analyses. Of course, the study isn’t perfect. Over-the-counter use may not have been fully captured, registry diagnoses can miss nuance, and differences between pregnancies (say, a fever in one but not another) could still matter.

This Swedish study is one of the strongest pieces of evidence we have so far. While early analyses suggested small increases in risk, those disappeared once family factors were accounted for. It reinforces that acetaminophen itself is unlikely to be the cause of autism or ADHD, and that the links seen in other studies are more likely due to underlying health reasons or genetics, not the medication alone.

What research can and can’t tell us in pregnancy

Beyond the Harvard review and the Swedish cohort, there are other studies you may see mentioned. Each adds a piece to the puzzle, but each also shows why research in pregnancy is complicated.

One study used what’s called a negative control exposure design. Instead of just looking at acetaminophen use in pregnancy, it compared patterns of acetaminophen use in and out of pregnancy to tease apart which associations might be due to unchanging factors like genetics or chronic illness. That design is clever, but it has limits. It can’t rule out time-specific pregnancy factors, like infections, new pain, or acute illness, that may both increase acetaminophen use and independently raise risk for conditions like ADHD. In other words, the study can’t fully prove whether the risk came from the medicine itself or from the circumstances surrounding its use.

Another study often cited is a cord-blood biomarker study. Instead of relying on self-report, it measured acetaminophen levels in umbilical cord blood at birth. That sounds objective and it is a step forward. But cord blood only captures exposure right around delivery, not across the whole pregnancy. Every sample in the study showed some exposure, so the researchers could only compare “higher” versus “lower” levels, not exposed versus unexposed. That makes it harder to interpret. And just like other observational studies, it can’t eliminate confounding by factors like maternal illness or genetic risk.

Together, these studies highlight both progress and challenge. Researchers are finding more creative ways to measure exposure, but pregnancy research will always have limits. We can’t run randomized trials asking pregnant people to take or avoid a medication that might cause harm. That means observational studies, each with blind spots, are what we have. The best approach is to weigh them together, look at the quality of their designs, and combine that evidence with clinical expertise and real-world context.

No single study can tell the whole story. Each brings useful insights, but each also comes with caveats. That’s why pregnancy care has to be based on the bigger picture, multiple studies, clinical judgment, and what makes sense for an individual parent’s health.

Closing thoughts

Taken together, the research on acetaminophen and autism is mixed, and that’s exactly why it sparks so much debate. Reviews and observational studies sometimes find small associations. Stronger designs, like sibling comparisons, don’t. Biomarker studies add interesting clues, but they only capture a snapshot in time. Each paper has something to offer, but none gives the final word.

That’s how science works. It builds slowly, piece by piece, and often the pieces don’t line up neatly at first. Interpreting those results is just as important as collecting them. For parents, the takeaway isn’t to chase every headline. It’s to remember that research is one part of care, meant to be weighed alongside your own health needs, your lived experience, and the guidance of your OB or pediatrician.

Being informed doesn’t mean carrying the burden of every study on your shoulders. It means having enough context to ask good questions, to understand where uncertainty lies, and to make decisions that fit your situation. Evidence is there to guide. Not to create guilt or fear.

Parents deserve nuance, clarity, and respect, especially with topics as emotionally charged as autism. If you’ve worried about these headlines, you’re not alone. And if you’ve taken acetaminophen in pregnancy, it doesn’t mean you did something wrong. It means you made the best choice you could with the information you had at the time. That’s what good parenting is: doing your best with what you know, and adjusting as you learn more.

On The Podcast

Politics and public health haven’t always been so divided, but in today’s world, even science and vaccines have become political battlegrounds. That’s why I sat down with Congressman Maxwell Frost, the youngest member of Congress and a voice for Gen Z leadership, to talk about where we go from here.

We dig into what it means to lead in such a polarized time, the dangers of politicizing health, and how younger generations can push for change. Congressman Frost opens up about his perspective on the vaccine mandate debate in Florida, the role of misinformation, and why community and courage matter more than ever.

Friendships after motherhood can feel complicated. Before kids, hanging out with friends might have been as easy as grabbing brunch or planning a last-minute outing. But now? Time, energy, and support look very different.

In this Follow Up episode, Dr. Mona revisits her conversation with relational health educator Danielle Bayard Jackson, author of Fighting for Our Friendships: The Science and Art of Conflict and Connection in Women’s Relationships. Together, they break down why building and maintaining friendships as a mom feels harder—and how to approach it with more grace and intention.

On YouTube

As a pediatrician and mom, I’m breaking down what’s really in baby formula…ingredients, safety, and what those labels actually mean. In this video, I explain formula regulation in the U.S., common myths about generic vs brand-name, and how formula compares to breast milk. If you’ve ever felt confused in the formula aisle, this guide will help you understand baby formula ingredients with clarity and confidence.

Ask Dr. Mona

An opportunity for YOU to ask Dr. Mona your parenting questions!

Dr. Mona will answer these questions in a future Sunday Morning Q&A email. Chances are if you have a parenting concern or question, another parent can relate. So let's figure this out together!