No scientific proof of link between paracetamol and autism: S'pore doctors

Doctors in Singapore said there is no scientific basis that acetaminophen, known as paracetamol here, causes autism when taken during pregnancy.

Acetaminophen or paracetamol is the active ingredient in Tylenol and Panadol, two brands of pain-relieving medication.

Professor Tan Hak Koon, chairman of the Division of Obstetrics and Gynaecology at KK Women's and Children's Hospital, told The Straits Times that paracetamol has been used safely in pregnancy for decades, and this is backed by leading medical organisations worldwide.

"Current scientific evidence does not support claims that acetaminophen or paracetamol causes autism when taken during pregnancy," he said.

Obstetricians and gynaecologists ST spoke to want to assure expectant women that paracetamol remains safe to use throughout pregnancy when taken at recommended doses for the shortest duration needed.

On Sept 22, US President Donald Trump had claimed there is a link between the use of Tylenol by pregnant women and an increased risk of autism in some children.

He went against current scientific advice and medical opinion by saying that taking Tylenol was "no good", and that pregnant women should "fight like hell" to take it only in cases of extreme fever.

His announcement came after months of widely trumpeted investigations spearheaded by his health secretary Robert F. Kennedy Jr, and was an assertion hotly contested by scientists and contradicted by studies worldwide.

International medical bodies hit back, with the World Health Organisation (WHO) being the most recent one. In a statement on Sept 24, the WHO emphasised that there is currently no conclusive scientific evidence confirming a possible link between autism and use of acetaminophen during pregnancy.

It said that globally, nearly 62 million people or one in 127 have autism spectrum disorder. Although awareness and diagnosis have improved in recent years, the exact causes of autism have not been established.

"Extensive research has been undertaken over the past decade, including large-scale studies, looking into links between acetaminophen use during pregnancy and autism. At this time, no consistent association has been established," it concluded.

Associate Professor Ho Han Kiat from the Department of Pharmacy and Pharmaceutical Sciences at NUS said paracetamol is the most well-studied medication of all time.

"It is the prototypical medication that research methodology, knowledge and understanding about adverse effects are based on. Therefore, evidence or the lack (of it) for specific side effects is well researched and supported by established scientific rigour... Existing data is plentiful to confirm or reject a presumptuous correlation," he said.

Prof Ho, who is one of the few local toxicologists certified by the American Board of Toxicology, said: "Paracetamol is metabolised by the body to generate a chemically reactive substance that attacks proteins in the liver. Such mechanism has not been demonstrated for causing neuronal changes that could lead to autism/ADHD or other related conditions."

The experts said the drug remains the best treatment for pain and fever during pregnancy.

Said Prof Tan: "In fact, untreated fever and severe pain during pregnancy can harm both mother and baby. Untreated fever has been associated with miscarriage, foetal organ malformations and cardiovascular complications, while unmanaged pain can lead to elevated blood pressure, stress and mental health issues that adversely affect pregnancy outcomes."

Dr Quek Swee Chong, an obstetrics and gynaecology specialist, said: "I have no problems prescribing Panadol (acetaminophen) for my pregnant patients for pain, headaches or fever and will continue to do so until there is a clearly identified causal link (to autism) and it has been thoroughly assessed by the FDA (Food and Drug Administration), HSA (Health Sciences Authority) and other authorities."

Dr Christopher Chong, an obstetrician and gynaecologist in private practice, said: "In prescribing to pregnant women, medications are given only when necessary, and we always start with those categorised as the lowest risks of harming the foetus." He added that there is no test at present to predict autism antenatally.

"Autism is a behavioural problem, and behavioural issues are multifactorial. To prove this, there must be huge randomised studies, but as it is not ethical or fair to subject a pregnant woman to tests which may harm the foetus, such tests cannot be done," he said.

Autism is a neurodevelopmental condition that is increasing in prevalence worldwide.

A large-scale landmark study in April 2024 by both Swedish and US researchers on 186,000 people demonstrated that there was no link between paracetamol use by expectant mothers and autism spectrum traits in their offspring.

The study, funded by the US National Institute of Health, looked at nearly 186,000 children whose mothers were treated with paracetamol during pregnancy, comparing them with their own brothers and sisters. It concluded that there was no evidence of a link between maternal paracetamol use and autistic traits.

In Singapore, there has been an exponential increase in autism-related research since 2010, when the first Singapore Clinical Practice Guidelines on autism were published.

A local study published in 2023 by the National University Hospital and National University Polyclinic found that more than one in 100 children at the age of 18 months in Singapore have autism - the age when children can be screened for the neurodevelopmental condition.

In a letter to ST, Dr Wong Chui Mae and Dr Aishworiya Ramkumar, who co-lead the Autism Clinical Practice Guidelines Workgroup at the Academy of Medicine, wrote: "Medical evidence to date, including subsequent publications in 2024-2025, shows that there is insufficient evidence for any association between maternal intake of paracetamol during pregnancy and the probability of autism in the child. This being so, mothers-to-be do not need to avoid paracetamol in pregnancy."

Said Prof Tan: "Our advice to pregnant women remains unchanged: If you need pain relief or have a fever, paracetamol is safe and appropriate to use.

"We encourage pregnant women to discuss any concerns with their healthcare provider, rather than avoiding necessary treatment based on unfounded concerns."