Doctors in the US will soon be advised not to prescribe the pain reliever Tylenol to pregnant women, US President Donald Trump said, citing a disputed link between the drug and autism.

The US president claimed on Monday that taking Tylenol, known as paracetamol elsewhere, "is no good" and that pregnant women should "fight like hell" to only take it in cases of extreme fever.

Medical experts have strongly pushed back on the claims, with some calling the president's comments dangerous.

Health officials in the UK have stressed that paracetamol remains the safest painkiller available to pregnant women.

UK Health Secretary Wes Streeting said: "I trust doctors over President Trump, frankly, on this."

The American College of Obstetricians and Gynecologists pushed back hard against Trump's announcement, which he made in the Oval Office on Monday.

Its president, Dr Steven Fleischman, said the claim of a link "is not backed by the full body of scientific evidence and dangerously simplifies the many and complex causes of neurologic challenges in children".

"Studies that have been conducted in the past, show no clear evidence that proves a direct relationship between the prudent use of acetaminophen during any trimester and fetal developmental issues," the statement added.

In a notice to doctors, the US Food and Drug Administration (FDA) used milder language than Trump.

The agency said doctors should consider limiting the use of Tylenol, while also taking into account that it is the safest over-the-counter option to treat fever and pain in pregnant women, which can also harm maternal and fetal health.

"To be clear, while an association between acetaminophen and autism has been described in many studies, a causal relationship has not been established and there are contrary studies in the scientific literature," the FDA wrote.

Speaking alongside Trump, Health Secretary Robert F Kennedy Jr said the FDA would also begin the process of initiating a safety label change on the medication and launch a public health campaign to spread awareness.

Tylenol is a popular brand of pain relief medication sold in the US, Canada and some other countries. Its active ingredient is acetaminophen, better known as paracetamol outside of North America.

The drug is recommended by other major medical groups as well as other governments around the world.

In a statement to the BBC, Tylenol maker Kenvue said the science clearly shows that taking acetaminophen does not cause autism.

"We strongly disagree with any suggestion otherwise and are deeply concerned with the health risk this poses for expecting mothers."

Kennedy added on Monday that the FDA would soon approve leucovorin, a decades-old drug traditionally used to protect cancer patients against toxicity from chemotherapy, to be used as treatment for children with autism.

FDA Commissioner Marty Makary said the approval will be based on research that he said suggests the drug may help children with autism who are deficient in folate, a form of vitamin B,improve their verbal communication.

But researchers have cautioned that the science is still in the very early stages, and more work is needed before any firm conclusions can be reached.

In April, Kennedy pledged "a massive testing and research effort" to determine the cause of autism in five months.

Trump on Monday called the rise in reported autism cases a "horrible crisis", and an issue that he has "very strong feelings about".

But experts have cautioned that finding the causes of autism - a complex syndrome that has been researched for decades - would not be simple.

The widely held view of researchers is that there is no single cause of autism, which is thought to be the result of a complex mix of genetic and environmental factors.

In August, a review of research led by the dean of Harvard University's Chan School of Public Health found that children may be more likely to develop autism and other neurodevelopmental disorders when exposed to Tylenol during pregnancy.

Out of 46 studies included in the review, 27 identified a positive link between taking Tylenol and children developing neurodevelopmental disorders.

Researchers argued some steps should be taken to limit use of the drug, but said it was still important for treating maternal fever and pain.

But another study, published in 2024, found no relationship between exposure to Tylenol and autism. It was conducted by looking at a population sample of 2.4 million children born in Sweden between 1995 to 2019.

"There is no robust evidence or convincing studies to suggest there is any causal relationship," said Monique Botha, a professor in social and developmental psychology at Durham University in the UK.

The National Autistic Society, a British group representing autistic people and their families, called Trump's claims about Tylenol and autism "irresponsible" and said he had devalued autistic people.

"The incessant misinformation about autism from President Trump and Robert F Kennedy Jr risks undermining decades of research by respected experts in the field," the group said.

Haley Drenon, a 29-year-old from Austin, Texas, who is pregnant for the first time, said the announcement made her nervous, as she had to take Tylenol during her first trimester for headaches.

"This announcement, if made without the proper context, would worry a lot of other people as well," she said. "It seems a little unnecessary just because the headlines are clear that the data is not irrefutable."

Autism diagnoses have increased sharply since 2000, and by 2020 the rate among 8-year-olds reached 2.77%, according to the US Centers for Disease Control and Prevention (CDC).

Scientists attribute at least part of the rise to increased awareness of autism and an expanding definition of the disorder. Researchers have also been investigating environmental factors.

In the past, Kennedy has offered debunked theories about the rising rates of autism, blaming vaccines despite a lack of evidence.

Trump has also promoted unsubstantiated medical claims, including during the Covid-19 pandemic.