A major study involving more than 1.5 million children in Denmark has found no evidence that taking acetaminophen during pregnancy is linked to a diagnosis of autism in offspring. The research, published in the journal JAMA Pediatrics on Monday, represents one of the largest and most robust investigations to date into a claim that has sparked significant political debate and public concern, particularly in the United States.
The weight of the Danish evidence
The study’s power lies in its scale and methodology, leveraging Denmark’s comprehensive national health registries to track every child born in the country between 1997 and 2022. Within this vast cohort, researchers identified 31,098 children who had been exposed to acetaminophen—known as paracetamol in the UK and sold under brands like Tylenol in the US—while in the womb. The analysis found autism was diagnosed in 1.8% of children with prenatal exposure, compared to 3% of those without, showing no statistically significant link. The study’s authors concluded, “Overall, our findings showed no association between the use of acetaminophen during pregnancy and risk of autism in offspring”.
This finding aligns with a growing body of international research that has struggled to find a causal link. A 2024 study in Sweden, analysing approximately 2.5 million children, also found no causal connection to autism or ADHD. Crucially, another Swedish study that year, involving over 2.4 million children, found that a marginal association observed in initial analysis vanished when sibling pairs were compared. This suggests shared familial, genetic, or environmental factors—not the drug itself—were responsible for the apparent signal, a point underscored by a 2025 review of pivotal evidence which concluded in utero exposure is unlikely to confer a clinically important increased risk of autism spectrum disorder.
US policy, politics, and the precautionary principle
These large-scale epidemiological findings stand in contrast to regulatory actions and political statements in the United States. On 22 September 2025, the US Food and Drug Administration (FDA) initiated a process to change the safety label for acetaminophen to reflect evidence suggesting a potential association with neurological conditions like autism and ADHD. In a letter to physicians, the FDA stated that while an association has been described in many studies, a causal relationship has not been established and contrary studies exist. FDA Commissioner Marty Makary said the agency was acting “to make parents and doctors aware of a considerable body of evidence about potential risks,” invoking the precautionary principle.
That same day, President Donald Trump explicitly cautioned against the drug’s use. “If you’re pregnant, don’t take Tylenol,” he said at a press conference. “Don’t take Tylenol. Don’t have your baby take Tylenol.” He claimed the medication was “not good” and associated with “a very increased risk of autism”. The Trump administration has targeted Tylenol use in pregnancy as a major cause of autism. At that September event, officials also announced that leucovorin, a B vitamin, could be used to treat autism—a claim the FDA later walked back, approving the drug only for a rare condition called cerebral folate deficiency.
The tangible impact on patient behaviour
The effect of these high-profile warnings has been measurable. According to a study published in The Lancet last month, orders of Tylenol for pregnant women in US emergency rooms dropped by 16% in the initial period following the September announcement. Jeremy Faust, a co-author of that study and an emergency physician at Mass General Brigham, stated that health officials’ “words are affecting behaviour”. He noted the rate of emergency orders dropped as low as 20% three weeks after the announcement, with no corresponding change for non-pregnant women or for other medications like opioids.
This shift concerns clinicians because acetaminophen is widely considered the safest option for pain and fever relief during pregnancy. Major medical bodies, including the UK’s Royal College of Obstetricians and Gynaecologists, the American College of Obstetricians and Gynecologists, and the International Federation of Gynecology and Obstetrics, all recommend it as the first-choice analgesic when clinically needed. The UK’s Medicines and Healthcare products Regulatory Agency has confirmed it has seen no evidence that paracetamol causes autism, a position echoed by the NHS, which recommends it for pregnant women. The drug’s manufacturer, Kenvue, has also consistently stated it believes there is no causal link.
Experts stress that untreated pain and fever carry their own risks for both mother and baby, and alternatives like ibuprofen are not generally recommended in pregnancy due to potential complications. “It’s the safest option for pain control and fever reduction,” Dr Faust said, expressing relief that the decline in acetaminophen use did not coincide with an increase in orders for riskier opioid painkillers.