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Claims including by President Donald Trump that the children of pregnant women who use paracetamol are at higher risk of developing autism is unsupported by the evidence, according to a comprehensive review of research to date.
The study published in the Lancet late on Friday found no clinically important increase in the likelihood of autism, ADHD or intellectual disabilities. The US leader and the health secretary Robert F Kennedy Jr had suggested that the drug can affect brain development.
The analysis of past work backs the advice of leading medical bodies that paracetamol is safe for use in pregnancy under existing guidelines. It warns that previous research papers alleging harms may be unreliable because they are prone to distortions.
“Public statements suggesting such a link risk overstating findings from earlier observational studies that were vulnerable to confounding and bias,” said Asma Khalil, the new paper’s senior author and a professor of obstetrics and maternal medicine at City St George’s, University of London.
“In that sense, those claims are not supported by the current scientific evidence, and they may understandably cause unnecessary anxiety among pregnant women.”
The study does not explicitly reference the political controversy over paracetamol, known as acetaminophen in the US. But it takes as its starting point that “concerns have emerged” about the drug’s impact.
The findings suggest familial and genetic factors, including the tendency for autistic traits to be seen in successive generations, are “more plausible explanations” for the appearance of the condition than “any direct effect of paracetamol”, the researchers said.
Khalil and her colleagues attempted to weigh previous research to exclude studies with possible biases, such as participants who incorrectly recalled their paracetamol consumption or suffered from other conditions that could have influenced their child’s health.
The studies used validated questionnaires or medical records, details of maternal health conditions and treatments, and compared pregnancies with and without paracetamol exposure.
The research gave the highest priority to large studies that compared outcomes for siblings, where the mother took paracetamol during one pregnancy but not the other.
Such a study design is intended to reduce the potential impact of differences between children due to factors such as parental genetics, socio-economic background and home environment.
How researchers assessed the studies
Stage 1
4,147 studies on paracetamol use by pregnant women were screened, of which 4,092 were excluded because the reported outcomes were not relevant
stage 2
55 full text articles were assessed, of which a further 12 were excluded for reasons such as relevance, design and lack of data
stage 3
43 papers were systematically reviewed, of which 17 high-quality studies were chosen for detailed statistical meta-analysis, with sibling comparisons prioritised
Khalil acknowledged limitations in her team’s work including the small number of studies to date that have used sibling or family-based designs.
If further useful research on paracetamol were to be done, it should delve deeper into reliably measurable factors such as the concentration of the drug in the blood, Khalil said.
Other scientists welcomed the latest review. It was “timely and well conducted” and gave a “justifiably robust” defence of paracetamol’s role as a treatment option for pregnant women with pain or fever, said Ian Douglas, a professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine.
In September, Trump linked the consumption of the branded paracetamol Tylenol during pregnancy to autism in children — a connection the drug’s maker, Kenvue, has denied.
In October, Kennedy said anybody who took paracetamol during pregnancy — unless they had to — was “irresponsible”. The administration was “doing the studies to make the proof” it caused harm, he added.
The paracetamol case has become a touchstone for critics who say some Trump administration health policies rely on the selective use of data, highlighting helpful studies while ignoring contradictory research.
The White House has cited Andrea Baccarelli, senior author of a paper published in August that said children exposed to paracetamol during pregnancy may be more prone to neurodevelopmental disorders.
Baccarelli, dean of the Harvard TH Chan School of Public Health, disclosed at the time that he had appeared as a witness for claimants in a lawsuit involving potential links between paracetamol use during pregnancy and neurodevelopmental disorders.
He was paid at least $150,000 for his work, according to court filings. The judge dismissed the case and backed the defence lawyer’s argument that Baccarelli had “cherry-picked and misrepresented” study results.
Baccarelli and the Harvard TH Chan School have been approached for comment.