Taking acetaminophen, the active drug in Tylenol, during pregnancy does not increase the risk of autism, according to one of the largest studies ever conducted on the issue.
In an analysis of more than 1.5 million Danish children, researchers found that prenatal exposure to acetaminophen was associated with just a three percent higher risk of autism in the general population — a difference that was not statistically significant.
Further, a sibling analysis comparing siblings with different exposure levels during pregnancy also found no meaningful association.
The findings directly push back against recent comments from Trump administration health officials, who have suggested a potential link between the common pain reliever and neurodevelopmental disorders.
The Danish team noted that even the upper limit of their statistical model ruled out anything more than a 12 percent increased risk, and that their results align with a 2024 Swedish study that also found no causal connection.
‘In this nationwide cohort study, acetaminophen exposure during pregnancy was not significantly associated with an excess risk of autism,’ the researchers wrote.
Autism spectrum disorder (ASD) is most commonly diagnosed in children around five years old.
One in 31 American children is on the spectrum, with symptoms ranging from tolerable sensory sensitivities to more debilitating speech or intellectual disabilities.
While research into the disorder’s exact causes is ongoing, experts in psychology, pediatrics and genetic medicine contend that ASD is largely genetic, with an estimated 60 percent to 90 percent of the risk being passed down through families.
Among 1.5 million Danish children, prenatal acetaminophen exposure was linked to a statistically insignificant three percent higher risk of autism (stock)
Dr Kira Philipsen Prahm, a researcher at Copenhagen University Hospital Rigshospitalet, Denmark, and lead author of the latest study, told MedPage Today: ‘Recent political statements, together with widespread media coverage, have directed attention to a potential link between acetaminophen and autism.
‘Given recent concerns, we found it relevant to make a well-performed study to either confirm or refute a potential association.’
Researchers analyzed data from more than 1.5 million children born in Denmark between 1997 and 2022.
They used national prescription records to identify which mothers filled a prescription for acetaminophen during pregnancy.
The study, published in JAMA Pediatrics, only included data on prescription acetaminophen ordered by a doctor.
The researchers could not track over-the-counter acetaminophen that mothers bought themselves without a prescription, which is how most people get Tylenol or other acetaminophen-containing products.
Children were followed from age one until July 2023 or until they received an autism diagnosis, whichever came first.
The team adjusted their findings for dozens of confounding factors, including the mother’s age, income, smoking habits, other medications and underlying health conditions.
There was still a lack of an association.
Of more than 1.5 million Danish children included, just over 31,000 were exposed to acetaminophen in the womb.
Among those exposed, 1.8 percent were later diagnosed with autism, compared to three percent in the unexposed group, a difference that vanished after researchers adjusted for those confounding factors.
Then, researchers analyzed sibling data to explore how the drug possibly impacted one sibling exposed to the drug and one who was not exposed.
The researchers identified families where a mother had at least two children but only took acetaminophen during one pregnancy and not the other. Then they compared those siblings.
Because siblings share the same genetics, same household environment and many of the same socioeconomic factors, any difference in autism risk between them is far more likely to be caused by an exposure itself.
The sibling analysis found no meaningful association between acetaminophen exposure during pregnancy and autism incidence.
Siblings exposed to acetaminophen in the womb were not more likely to develop autism than their unexposed brothers or sisters.
Despite decades of research, medical experts and organizations saying acetaminophen use during pregnancy is safe, Trump administration health officials, led by Health and Human Services Secretary Robert F Kennedy Jr. have cast doubt.
In a press briefing in September 2025 in which the president and health leaders claimed a link, RFK Jr said that ‘the FDA is responding to clinical and laboratory studies that suggest a potential association between acetaminophen used during pregnancy and adverse neurodevelopmental outcomes, including later diagnosis for ADHD and autism.’
However, they did not specify which studies. A 2025 review of past research did suggest a possible link between the drug and autism but the researchers said it did not prove causation and said pregnant women should continue using acetaminophen as needed, at the lowest dose and for the shortest time possible.
RFK Jr has made autism a central focus of his public messaging, often attributing higher-than-global-average rates in the US to environmental triggers without robust evidence.
And President Donald Trump has echoed RFK Jr’s skepticism of mainstream medical consensus, warning pregnant women at that press briefing: ‘I’ll say it: It’s not good. Don’t take Tylenol. Fight like hell not to take it.’
Today, about 1 in 31 children in the US has an autism diagnosis — roughly three percent of all children. That rate has climbed steadily in the past two decades. In the year 2000, the year monitoring began, the rate was just 1 in 150.
The main reason for the spike is that experts have gotten much better at identifying autism.
The definition of autism has expanded to include milder forms, including what used to be called Asperger’s syndrome, and doctors now actively screen all young children for it.
Acetaminophen is the active drug in Tylenol and other common over-the-counter cold, flu and pain relievers
In the past, many of these children would have been missed or given a different diagnosis, such as an intellectual disability.
While changes in awareness and diagnosis explain most of the rise, some experts believe there might be a small, real increase in the condition itself.
Possible reasons for this include more parents having children at an older age and certain prenatal factors. However, the scientific debate on that point is still open.
The first signs of autism typically emerge between 12 and 24 months of age, often catching parents’ attention when a child misses key developmental milestones, like limited eye contact, lack of response to their name, no pointing or waving by 12–18 months, as well as repetitive behaviors.
According to the NIH, some children may even experience a regression, losing language or social skills between 15 and 24 months.
Social skills, such as eye contact, smiling, responding to their name and imitation, are also frequently lost.
An estimated 20 percent of children with ASD experience this form of regression.
A baby who does not make big smiles by six months, share sounds back and forth by nine months, babble or gesture by 12 months or speak by 16 months exhibits red flags that parents should raise with their pediatrician.
Other common early signs include delayed speech, repetitive movements such as hand-flapping or rocking, intense fixation on specific toys or objects, and difficulty with pretend play.
For now, the advice to expectant mothers remains unchanged. When used as directed, acetaminophen is still considered safe for managing fevers and pain during pregnancy.
