By Helen Johnson

Copyright channel4

President Donald Trump has claimed that there’s a link between women taking paracetamol during pregnancy and their children having autism.

He said at the White House on Monday the medication is “not good” and that “for this reason” the US Food and Drug Administration is “strongly recommending” that women “limit” its use during pregnancy “unless medically necessary”.

This comes after he said on Saturday: “I think we found an answer to autism” and White House Press secretary Karoline Leavitt told journalists that there is “mounting evidence finding a connection between [paracetamol] use during pregnancy and autism”.

Let’s take a look.

The key terms

We’re going to look at a number of studies in this article – so here are some of the key terms you’ll need to make sense of them.

Tylenol is the brand name for paracetamol in the US. Acetaminophen is the technical name for paracetamol and is commonly used in scientific research and reports.

Autism can cause difficulties with social interaction and communication. Attention deficit hyperactivity disorder (ADHD) can cause inattention, hyperactivity and/or impulsivity. Hyperkinetic disorders cause excessive, involuntary movements.

Many of the studies into a potential link between paracetamol and autism look at correlation, which is where two things happen at the same time. What’s much harder to prove is causation: a clear, definitive, provable link where one thing directly causes another.

And you might see “confounding variable” mentioned, which can affect the result of a scientific experiment and make it less clear that one thing causes another.

What evidence has the White House put forward to suggest a link between paracetamol and autism?

Mr Trump’s claims don’t seem to be based on one specific report or set of findings, but the White House released a list of studies he appears to be relying on.

The first one mentioned uses data from the Nurses’ Health Study II, which was published in 2019 and looked at paracetamol and ADHD – not autism. The analysis found that children whose mothers took paracetamol regularly throughout pregnancy, which was defined as more than twice a week, were around a third more likely to be diagnosed with ADHD compared to children who were not exposed to the drug in the womb.

But Dr Monique Botha, an associate professor in social and developmental psychology at Durham University, told FactCheck that this study “is still an observatory study which cannot effectively evaluate causation”, and that is has “confounding factors not controlled for, and which sits lower down the evidence pyramid in terms of quality”.

She said that it’s more instructive to look at a 2024 Swedish study which “controlled for genetic variability and family history by doing sibling case control and showed no relationship to ADHD”.

“That is the most robust data we have on this because it is a study that directly evaluates causation,” she added.

Another report mentioned by the White House was published last month by a group of researchers at a number of US universities, including Harvard.

The research looked at 46 previous studies conducted on this topic and said its analysis “demonstrated evidence consistent with an association between exposure to acetaminophen during pregnancy and offspring with neurodevelopmental disorder”, including autism and ADHD.

But it added that “observational limitations preclude definitive causation”. In other words, the studies in the analysis cannot prove that paracetamol has caused children to develop these conditions.

And although the researchers recommended “judicious” use of the drug during pregnancy, the report said it is still important for treating pain and fever during pregnancy – which can also pose risks to both mother and baby if left untreated – so a “balanced approach” is needed.

What does other scientific literature say about paracetamol and autism?

The question of whether paracetamol taken during pregnancy could be a cause of autism in children is something which has been looked into by scientific experts over many years.

Dimitrios Siassakos, professor in obstetrics and gynaecology at University College London, told the Science Media Centre this week that autism “results from several factors, often combined, particularly genetic predisposition, and sometimes low oxygen at the time of birth as a result of complications”.

He added that research has shown that “any apparent marginal increase” as a result of paracetamol use in pregnancy “tends to disappear when the analyses take into account the factors that matter most”.

Prof Siassakos said in the research into this topic “it was the family history that mattered and not the use of paracetamol”.

This is shown in the Swedish study 2024, that we looked at before in relation to ADHD. The researchers examined 2.4 million births over a period from 1995 to 2019. Although it found a marginal increase in the risk of autism, when the researchers included data for siblings born to the same mothers from pregnancies during which she took no paracetamol, the apparent link disappeared.

This suggests that the initial correlation between paracetamol and autism was likely due to confounding variables, such as genetics or family environment, and is not a direct causal effect of the medication.

Dr Viktor Ahlqvist at the Karolinska Institute in Stockholm, who led the study, said this “provides pretty strong evidence against the notion that paracetamol would cause harm”.

Like Prof Siassakos and Dr Ahlqvist, Dr Botha mentions the sibling aspect of the study. She said the study using “actual sibling data” and finding “no relationship between exposure to paracetamol in utero and subsequent autism, ADHD or intellectual disability” suggests “no causal effect”.

FactCheck also asked Dr Botha about a Danish study published in 2015, which followed over 64,000 children and mothers for nearly 13 years. It found that “prenatal use of acetaminophen was associated with an increased risk of autism accompanied by hyperkinetic symptoms”.

But Dr Botha noted that the Danish research was “merely correlational and that is not the appropriate way of understanding complex causality”.

It’s also worth noting that even studies that appear to show a correlation between taking paracetamol and autism are only looking at the possibility of elevated risk. They are not saying that everyone who takes it during pregnancy will have a child who is later diagnosed with autism or any other condition examined in the study.

Dr Alison Cave, chief safety officer at the UK’s Medicines and Healthcare products Regulatory Agency (which regulates medicines, medical devices and blood components for transfusion), said: “Patient safety is our top priority. There is no evidence that taking paracetamol during pregnancy causes autism in children.

“Paracetamol remains the recommended pain relief option for pregnant women when used as directed.”