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The U.S. Food and Drug Administration on Monday announced plans to update the labeling of acetaminophen products, citing a “possible association” between prenatal use and neurodevelopmental disorders such as autism. During a White House press conference, President Donald Trump went further, bluntly warning the public, “Don’t take Tylenol,” and urging pregnant women to “fight like hell not to take it.”
But does the evidence support a causal link between acetaminophen and autism? While current research does not establish that acetaminophen use during pregnancy causes autism, a growing number of studies provide evidence of a concerning association between the two.
A comprehensive analysis published in the scientific journal Environmental Health in August concluded that children exposed to acetaminophen in the womb may face a heightened risk of developing neurodevelopmental disorders, including autism and attention-deficit/hyperactivity disorder (ADHD). The study systematically reviewed 46 existing studies and found that most of the higher-quality research reported a statistically significant association between prenatal acetaminophen use and increased rates of these conditions in offspring.
Acetaminophen, also known as paracetamol, is widely considered a go-to option for pain and fever relief during pregnancy. Over half of pregnant women around the world use the drug, often due to its safety compared to alternatives like non-steroidal anti-inflammatory drugs, which are known to carry teratogenic risks. However, over the past decade, several studies have raised questions about whether frequent or prolonged exposure to acetaminophen during pregnancy could disrupt the developing brain.
The brain undergoes rapid and sensitive developmental processes during gestation, and this makes it particularly susceptible to environmental influences—including medications. Given acetaminophen’s known ability to cross the placental barrier and interact with systems involved in hormone regulation, immune signaling, and oxidative stress, researchers aimed to determine whether consistent patterns exist between its prenatal use and later diagnosis of neurodevelopmental disorders.
“We decided to look into this because acetaminophen, like Tylenol, is something over half of pregnant women use worldwide for pain or fever, and it’s often seen as the safest option,” said study author Diddier Prada, an assistant professor at the Icahn School of Medicine at Mount Sinai.
“But we started noticing that some studies were hinting that it might be linked to kids developing issues like autism or ADHD later on. This got our attention because pregnancy is such a critical time for a baby’s brain to grow, and we wanted to figure out if this common medicine could be playing a role. With so many families relying on it, we felt it was important to dig deeper and get a clearer picture using a careful, step-by-step methodological approach.”
The researchers employed the Navigation Guide, a systematic methodology developed to assess environmental health risks through observational data. They searched PubMed, ISI Web of Science, and Google Scholar through February 2025 for studies examining links between prenatal acetaminophen exposure and neurodevelopmental outcomes. The focus was on children diagnosed with ADHD, autism, or related developmental challenges, and the review included both prospective and retrospective studies, some of which used biological markers such as acetaminophen levels in cord blood or meconium.
A total of 46 human studies met the inclusion criteria. These included large-scale cohort studies, sibling-controlled studies, and case-control designs. The researchers excluded animal studies and duplicated datasets. Each study was evaluated for its methodological quality, potential sources of bias, and strength of evidence. The team applied structured rating systems to judge how well each study accounted for key confounding variables, such as maternal age, chronic illness, substance use, and reasons for taking acetaminophen in the first place.
Due to significant variation in study designs, exposure measurements, and outcome definitions, the researchers opted not to conduct a meta-analysis. Instead, they synthesized the findings qualitatively, placing special emphasis on studies with stronger methodological rigor and prospective designs.
Of the 46 studies included, 27 reported positive associations between prenatal acetaminophen use and neurodevelopmental problems in children. Nine studies found no significant relationship, while four reported possible protective effects, and the remainder produced mixed findings. Importantly, the strongest associations were observed in studies with more rigorous designs—those that used biomarkers to assess exposure, adjusted for a wide range of confounding variables, and tracked participants over time.
For ADHD specifically, 14 out of 20 studies found a significant link between acetaminophen exposure in the womb and increased diagnosis rates. In some cases, a dose-response pattern emerged, suggesting that longer or more frequent use of the medication may elevate risk. For autism, five out of eight studies reported a positive association. Studies that examined other forms of neurodevelopmental disruption, such as language delays or behavioral dysregulation, also tended to find increased risk linked to prenatal acetaminophen use.
“We were a bit surprised by how many of the 46 studies we looked at—over half—showed a connection between acetaminophen use and these brain development issues, especially when the studies were well done,” Prada told PsyPost. “We also didn’t expect that a few studies suggested it might even help a little, though that was rare. The fact that the best studies kept pointing to a link was eye-opening and made us realize this is something we can’t ignore, even though it’s a medicine so many trust.”
The researchers also looked at evidence from sibling-controlled studies, which aim to account for shared genetic and environmental factors within families. These studies produced mixed results, with some showing null associations. However, the authors caution that sibling designs may suffer from reduced statistical power and higher susceptibility to certain types of measurement error, especially when exposure is based on self-reported data.
The consistency of findings across multiple cohorts, countries, and methods—combined with emerging evidence from biological studies—led the authors to conclude that the observed associations are unlikely to be explained solely by confounding factors. Laboratory studies and animal models have shown that acetaminophen can influence hormone signaling, immune function, and oxidative stress in ways that could plausibly interfere with brain development.
“The main thing people should know is that our research suggests using acetaminophen during pregnancy might affect a child’s brain development, possibly increasing the chance of conditions like autism or ADHD,” Prada explained. “It’s not a definite cause, but it’s a signal to be careful. If you’re pregnant or planning to be, it’s smart to use it only when you really need to, in small amounts and for a short time, and chat with your doctor about it. Untreated pain or fever can also harm the baby, so it’s about finding the right balance, and doctors are the best guides for that.”
While the review provides a strong argument for caution, it does not claim that acetaminophen causes neurodevelopmental disorders. The authors note that observational studies, no matter how well-designed, cannot definitively establish causality. Unmeasured confounding factors, such as maternal stress or infection, might still play a role in the observed associations.
Another limitation is that the studies included in the review varied widely in how they measured acetaminophen exposure—some relied on maternal recall, while others used biomarkers or medical records. Timing of exposure also varied, and some studies lacked detailed data on dosage or frequency. This heterogeneity makes it difficult to identify specific windows of heightened vulnerability or safe thresholds of use.
“Since all the studies we reviewed were observational—meaning they watched people rather than testing something directly—we can’t say for sure that acetaminophen causes these issues; it might be something else, like the reason for taking it, like a fever, playing a part,” Prada noted. “Also, some studies relied on moms remembering what they took, which isn’t always accurate, and the studies varied a lot in how they were done. So, while the evidence is strong enough to raise concern, it’s not the final word, and more research is needed to be certain.”
“Looking ahead, we want to do more detailed studies that follow bigger, more varied groups of people over time, checking things like traces of acetaminophen in babies’ bodies to see the impact on neurodevelopment in the children. Our goal is to figure out if this link is real and why it might occur, so we can protect kids’ brain development. We also hope to find safer ways to help pregnant women with pain or fever, like new medicines or other non-pharmacological approaches, like cool cloths, and work with doctors and health groups to update advice based on what we learn.”
“We’re really proud that this is the first time we’ve used such a careful method to pull together all this information, giving a clearer view than ever before,” Prada added. “It’s a team effort with experts from places like Mount Sinai, Harvard, UCLA, and UMass Lowell. We’re excited to see it spark conversations about how to keep moms and babies healthy. We also want to make sure everyone, especially those who might not have easy access to good healthcare, gets the message and support they need, because this is about fairness in health for all families.”
The study, “Evaluation of the evidence on acetaminophen use and neurodevelopmental disorders using the Navigation Guide methodology,” was authored by Diddier Prada, Beate Ritz, Ann Z. Bauer, and Andrea A. Baccarelli.
[Note: A previous version of this article was published on August 25, 2025.]
