PARIS, France (AFP) — There is no clear link between pregnant women taking the common painkiller paracetamol and autism in their children, despite repeated claims otherwise by Donald Trump, according to the most comprehensive review of the existing evidence published Monday.

In September, the US president sparked outrage among the medical community by claiming that paracetamol — also known as acetaminophen — was associated with higher rates of autism.

Trump urged pregnant women to “tough it out” rather than take paracetamol, comments which health researchers warned could scare women off their safest option to treat pain — and risked further stigmatizing autistic people.

The World Health Organization has emphasized that there is no robust evidence showing that paracetamol — which is the main ingredient in massively popular painkillers such as Tylenol and Panadol — causes autism.

On Monday, an “umbrella” review of all the scientific research yet conducted on the subject was published in the British medical journal BMJ.

“Existing evidence does not show a clear link between in utero exposure to paracetamol and autism and ADHD ( attention deficit hyperactivity disorder) in offspring,” the United Kingdom-lead team of researchers wrote in the review.

There have been several previous studies which suggested a possible link between paracetamol and autism or ADHD.

However the quality of those studies was “low to critically low,” the review said, partly because they did not take adequate steps to rule out potentially misleading factors such as whether autism runs in the family.

These controversial previous studies also could not establish exactly how paracetamol might cause autism.