Scientists are warning that one of the most trusted painkillers used in pregnancy may not be as safe as once believed.
A sweeping review of studies finds links between prenatal acetaminophen exposure and higher risks of autism and ADHD in children. The medication crosses the placenta and may interfere with brain development, raising urgent questions about clinical guidelines.
Acetaminophen in Pregnancy Linked to Neurodevelopmental Risks
Scientists at the Icahn School of Medicine at Mount Sinai report that children exposed to acetaminophen before birth may face a greater chance of developing neurodevelopmental conditions such as autism spectrum disorder and attention-deficit/hyperactivity disorder (ADHD). Their findings, published in BMC Environmental Health, mark the first time that the Navigation Guide methodology has been applied to thoroughly assess the quality and reliability of the research on this subject.
Acetaminophen (commonly sold as Tylenol® in the United States and Canada, and known as paracetamol elsewhere) is the most widely used non-prescription treatment for pain and fever during pregnancy, taken by more than half of expectant mothers worldwide. For decades, it has been viewed as the safest option for relief from headaches, fever, and general pain. However, the Mount Sinai team’s review of 46 studies, which together involved over 100,000 participants from multiple countries, challenges this long-standing belief and highlights the importance of caution and additional investigation.
Gold-Standard Review Methodology Applied
The research team relied on the Navigation Guide Systematic Review, a leading framework used in environmental health. This method enables scientists to systematically evaluate each study, rating potential sources of bias such as incomplete data or selective reporting, while also weighing the overall strength and consistency of the evidence.
“Our findings show that higher-quality studies are more likely to show a link between prenatal acetaminophen exposure and increased risks of autism and ADHD,” said Diddier Prada, MD, PhD, Assistant Professor of Population Health Science and Policy, and Environmental Medicine and Climate Science, at the Icahn School of Medicine at Mount Sinai. “Given the widespread use of this medication, even a small increase in risk could have major public health implications.”
Possible Biological Mechanisms Behind the Link
The paper also explores biological mechanisms that could explain the association between acetaminophen use and these disorders. Acetaminophen is known to cross the placental barrier and may trigger oxidative stress, disrupt hormones, and cause epigenetic changes that interfere with fetal brain development.
While the study does not show that acetaminophen directly causes neurodevelopmental disorders, the research team’s findings strengthen the evidence for a connection and raise concerns about current clinical practices.
Call for Updated Guidelines and Safer Alternatives
The researchers call for cautious, time-limited use of acetaminophen during pregnancy under medical supervision; updated clinical guidelines to better balance the benefits and risks; and further research to confirm these findings and identify safer alternatives for managing pain and fever in expectant mothers.
“Pregnant women should not stop taking medication without consulting their doctors,” Dr. Prada emphasized. “Untreated pain or fever can also harm the baby. Our study highlights the importance of discussing the safest approach with health care providers and considering non-drug options whenever possible.”
Rising Autism and ADHD Rates Add Urgency
With diagnoses of autism and ADHD increasing worldwide, these findings have significant implications for public health policy, clinical guidelines, and patient education. The study also highlights the urgent need for pharmaceutical innovation to provide safer alternatives for pregnant women.
Reference: “Evaluation of the evidence on acetaminophen use and neurodevelopmental disorders using the Navigation Guide methodology” by Diddier Prada, Beate Ritz, Ann Z. Bauer and Andrea A. Baccarelli, 14 August 2025, Environmental Health.
DOI: 10.1186/s12940-025-01208-0
The study was conducted in collaboration with the University of California, Los Angeles; University of Massachusetts Lowell; and Harvard T.H. Chan School of Public Health.
Funding for this study was provided by the National Cancer Institute (U54CA267776), the National Institute of Environmental Health Sciences (R35ES031688), and the National Institute on Aging (U01AG088684).
Important: These findings indicate a correlation, not definitive proof of causation. The medical community remains divided, and further research is needed. Always seek guidance from your healthcare professional before altering or discontinuing any treatment.
Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.
24 Comments
Amazing. Autism was first recorded in 1943. Acetaminophen aka Tylenol wasn’t sold until 1955. Quit bowing to fascism.
Your politics may be clouding your judgment.
Tylenol is indeed a brand of acetaminophen that was first sold in 1955. However, acetaminophen was first synthesized in 1878 and sold as a pain and fever treatment since 1893.
This article IS problematic. It only mentions correlation after running wild with the same alarmism pushed by certain politicians… that happened to give themselves a September deadline…
There is no evidence of causation. In fact scientists involved in the studies reviewed say as much. The risk of prolonged fever to the fetus however is proven and quite real.
https://www.npr.org/2025/09/23/nx-s1-5551030/the-science-behind-the-correlation-between-autism-and-tylenol
At this point, with the studies and evidence we have, we might as well say there’s an alarming correlation between owning furniture and the rising rates of broken toes. Don’t buy that sofa people!
If you drink excessive amount of water, it can also kill you, should we ban water? Shame on the publishers for a half baked article with many maybes and caveats, pretending to be scientifically rigorous.
I’m curious to know more specific details on what chemicals in Tylenol actually affect the brain. Maybe it’s still being studied out, but I can’t wait to see more info other than “there may be a link.”
Also, I’m wondering if the age of the parents was considered during these studies?
Yes, it appears maternal age and other key confounders were considered overall. You can see more in the actual study’s “discussion” section, and the sections leading up to it regarding risk-of-bias assessment. “Studies were rated as higher risk of bias (score of 3 or 4) if they lacked adjustment for key confounders, such as maternal age, chronic illness, socioeconomic status, smoking, alcohol use, or clinical indications for acetaminophen use (e.g., fever or infection).” // “Our Navigation Guide-based evaluation of the existing literature showed a strong, consistent association between prenatal acetaminophen exposure and ADHD/ASD/other NDDs. These studies were controlled for multiple potential confounders that might have plausibly explained the associations, yet the associations persisted.”
This isn’t about politics. It’s about confusion. The ACOG is filled with physicians who monitor drug safety in pregnancy and care passionately about this topic and spend all day every day working with pregnant women and delivering babies for years and years of their lives, monitoring outcomes, watching for trends, updating medication safety guidelines frequently when new information comes to light. Yet somehow all of these physicians missed this or somehow covered it up? It doesn’t make sense.
The reason pregnant women take acetaminophen is to reduce fever. Has this study looked at the role of fever and the illnesses that lead to fever as a possible causes for poor neurodevelopmental outcomes and children. This is the prime example of correlation not causation.
I don’t care that it was Trump that broke the news to the general public. To be sure, he’s an idiot who can’t pronounce anything longer than “you’re fired”. But, having said that, at least he’s got the discussion going.
We, as a collective, need to learn that no drug is safe, no matter how commonplace or ubiquitous it is. People are taking drugs like candy nowadays, and many of those drugs are OTC. That needs to change.
Well said. Agree 100%
My mind keeps going back to two facts:
— tylenol is deadly at higher levels for adult humans (taking more than 8 pills in one day can blow out your liver and kill you)
— one pill can kill a cat or dog
Why people are angrily resisting this idea that tylenol isn’t as safe as we were told, is beyond me.
Because billions of people have used acetaminophen/paracetamol as directed with benefit and safety for decades- including hundreds of millions of pregnant women without having children with autism. Given the sheer frequency of acetaminophen use as a pain and fever reducer by pregnant women, given that it is about the only medication considered safe for that purpose for them), if it was the cause of autism there would be far more autism than there is.
One of the reasons that there has been an apparent increase in autism diagnoses is that the diagnostic criteria were broadened dramatically with the creation of “autism spectrum disorder.” The changes in diagnostic guidelines resulted in many more children meeting that criteria and getting the diagnosis. This explains most if not all of the apparent increase in the prevalence and incidents of autism. Something similar happened with attention deficit disorder diagnoses.
Any medication that has therapeutic efficacy has the potential for harm, especially if that medication is misused. The combination of acetaminophen and alcohol, for example, is the leading cause of kidney failure. The acetaminophen label explicitly states not to use the medication while having three or more alcoholic drinks per day (these are probably standardized drinks, and one drink at a bar may easily equal three standard drinks; somebody might have two or three of those and then go home and take acetaminophen). Taking more than 4000 mg of acetaminophen from all sources per day can result in liver failure; most pharmacists and doctors recommend a 3000 mg a day maximum in order to provide a margin of safety, especially in older patients.
When a study comes along, such as this, which contradicts decades of research, then that study needs to be scrutinized and replicated carefully. Usually when somebody makes a dramatic reversal compared to the knowledge base, somewhere in their study they have made errors. Sometimes the new study is right, most often it is not.
Sorry, liver failure not kidney failure. Should proofread more carefully before I click the button.
I used to take the explanation that attributes the increased incidence of autism to the broadened definition of it. But the release date of DSM-IV, that is said to be the culprit, in no way coincides with the period when the increase in autism diagnoses reall took off.
And when the DSM-V, with some restrictions reinteoduced, was issued, it didn’t hel decrease the rate of autism diagnoses.
So, the causes are to be looked for elsewhere. I’m not saying it’s tylenol per se. It might as well be. It may be the next generation of adjuvants that are put into vaccines. Who knows at this point, right? It’s not like the Big Pharma is in any hurry to investigate itself, is it?
It’s because we don’t trust the messenger. RFK is an ignoramus, the most unqualified head of HHS in history. He has his own reasons for making people distrustful of Tylenol and they have nothing to do with MAHA.
The nutritional supplements industry is as large or larger than the OTC pharmaceutical industry. Billions of dollars are spent every year in America on unproven, unregulated supplements that are as likely to be harmful as beneficial. When carefully analyzed, supplements often don’t even contain the alleged active ingredient on the label and instead contain other things (including pharmaceuticals that should not be present). When the supplement does contain the alleged active ingredient, it can have a fraction of the dose on the label or it can have multiple times the dose on the label; this is not an industry that is rigorous in its manufacturing processes.
But to paraphrase your own argument from another reply: billions of people are taking supplements with no adverse effects taking place. So why worry, right?
No drug that is effective is safe. If it has efficacy, it has the potential to harm.
However, there are so many confounds to this story that it is difficult to accept the results of this study at face value. The person heading the US health department is a fervent anti-vaccine believer who is little troubled by facts or reality in the pursuit of forcing his beliefs upon others. Since he couldn’t successfully pin the cause of autism on vaccines, despite decades of trying, he looked around for another culprit to blame in order to meet his self impose of deadlines of explaining the cause of autism by September.
It will be interesting to watch the inevitable litigation around this. Every mother of an autistic child is going to be suing the manufacturers of Tylenol and generic acetaminophen with the largest class action lawsuits ever seen. The manufacturers of Tylenol and generic acetaminophen are going to be the federal government. The courts will be busy for years based on this. The advantage here is that courts are adjudicated upon facts, unlike public opinion; those claiming that acetaminophen causes autism are going to have to prove it with facts in court. We will see if they can do so.
… going to be *suing* the federal government, not “going to be the federal government.” Sorry!
Even if they can’t prove it in court, that won’t mean anything. Something can be true without the ability to prove that it’s true. Example: No one has proven there is a god. No one has proven there is no god. Yet one of those possibilities must be true.
Proving that there is no God is a logical impossibility (proving a negative is essentially impossible; the best that can be shown is that there is no evidence). The onus is on proving the positive statement, that there is a God. That has been elusive, so what can be stated is “there is no objective proof of the existence of God.” That, of course, does not stop billions of people from choosing to believe that there is a God. Belief does not require proof or facts.
The ability to prove or disprove in a court of law, however, is significant. In order for lawsuits against the manufacturers of acetaminophen/paracetamol to prevail, they will have to be able to demonstrate to the court that there is solid proof that the medication is a cause of autism and autism spectrum disorders. A single study such as this one is not going to be adequate because of limitations in the study. Unfortunately, this kind of study is prone to confusing correlation with causation and in this case appears to be politically directed to do so.
What if they do? Will you change your tune then?
The best study to date found a 1.5% chance of autism if no tylenol and 1.7% with tylenol. However, that difference disappeared if they controlled for siblings. Trump hip shot off the mark this time. As best I can determine the diagnosis of Autism grew as the diagnostic criteria expanded over and over again. Acetaminophen has not been shown to cause genetic birth defects. And my mother was very careful NOT to take any drugs during pregnancy, after a failed pregnancy left her shaken. I hit the diagnostic criteria quite solidly. And everything I have learned of my father who died when I was quite young suggest he had periodic autistic burnouts as he was starting a new heat treating oven company based on his patents.
I see three factors in the increased diagnosis.
1) Diagnostic criteria have been getting broader and broader with time as more conditions get lumped under autism rather than separate labels.
2) Awareness of Autism has increased dramatically. Why, ‘They’ are even suddenly recognizing that girls can be autistic and mask extraordinarily well, too.
3) The stigma of Autism has decreased incredibly. It’s safer to be diagnosed today than 80 years ago when I was little. Thank God I mostly fit the old Aspergers profile and learned to mask, to avoid stern parental disapproval, very well.
Bonus 4) It’s a new disease. Doctors feel excitement when “I found an autistic child. Oh goody! I score points and get to see how it works.” (Color me excessively cynical after 81 years of their tender mercies.) I figure this may lead to significant over diagnosis.
Bonus 5) I suppose I, discovered finally last year, count as a new case not one that was missed over 70 years ago.
And, very likely, Tylenol does NOT cause autism. It may cause fetal brain damage. If that brain damage could mimic any of the older familiar Autistic profiles I’d be very surprised. Mental deficits, yes. Hyperfocus, monotropism, very high performance within interest profiles – probably not.
{^_^}
The criteria has first been expanded in the 70s, and then restricted in the 90s. The rate of diagnosis kept growing unabated.
So, as plausible as that explanation seems, it’s likely balooney.
Thanks for your comments.
With folks like Temple Grandin being public about their autism spectrum disorder and also being world class experts in their field, autism is no longer seen as being necessarily severely disabling. I have worked with folks with ASD who were very, very good at their jobs. A little quirky perhaps, but successful. Often their biggest problems were how others reacted to those quirks.
The underpinnings are complex: genetic traits inherited from parents, mutations in genes occurring sporadically, suppression or activation of various genes by environmental factors, etc. If acetaminophen is a factor, that signal is going to be obscured among hundreds of other potential contributors. Parents looking for answers are likely to not want to hear it, but the genetic explanation of autism is actually the strongest.