Pregnant women should only take paracetamol when told to by a doctor, scientists have ruled.
Experts fear the cheap painkiller could raise the risk of their child having autism and attention deficit hyperactivity disorder (ADHD).
Dozens of studies have already linked paracetamol, known as acetaminophen in the US, to the two neuropsychiatric conditions.
But US scientists, who analysed the health records of over 100,000 people, claimed their analysis was the most comprehensive to date and showed there was 'strong evidence' to link the two.
In a call to action, they suggested mothers-to-be only get the 'lowest effective dose for the shortest possible time'.
However, it 'does not show that acetaminophen directly causes neurodevelopmental disorders', the scientists noted.
Further studies are first needed to examine how exactly how the drug may affect babies in the womb.
Dr Diddier Prada, an assistant professor of population health science at Mount Sinai Hospital in New York and study co-author said: 'Our findings show that higher-quality studies are more likely to show a link between prenatal acetaminophen [paracetamol] exposure and increased risks of autism and ADHD.
'Given the widespread use of this medication, even a small increase in risk could have major public health implications.'
But he added: 'Pregnant women should not stop taking medication without consulting their doctors.
'Untreated pain or fever can also harm the baby.
'Our study highlights the importance of discussing the safest approach with health care providers and considering non-drug options whenever possible.'
The NHS says paracetamol is paracetamol is safe to take in pregnancy, describing it as the 'first choice' painkiller for mothers-to-be but only over short periods.
Around half of expectant mothers report taking paracetamol during pregnancy, and the figure is as high as 65 per cent in the US.
Health chiefs say only certain people need to take 'extra care', such as patients with liver or kidney problems and those on epilepsy drugs.
In the study, researchers including those from Harvard University, analysed data from 46 studies involving over 100,000 people.
They collected data on when the paracetamol was taken—in the first, second, third trimester or across the full pregnancy—and looked at mothers medical records.
Writing in the journal Environmental Health, the researchers said: 'Ultimately, the obtained scores suggest strong evidence of a likely relationship between prenatal acetaminophen use and increased risk of ADHD in children.
'This includes high-quality studies that provide very strong evidence of an association and studies that provide strong evidence of an association.'
They added: 'There was strong evidence of a relationship between prenatal acetaminophen use and increased risk of autism in children'.
It comes as data released earlier this year revealed that the number of children seeking help for suspected autism has spiralled to an all-time high in Covid's wake.
Almost 130,000 under 18s in England were still awaiting an assessment in December 2024, NHS figures showed.
Experts have long warned that young people are facing an an 'invisible crisis', with a system that has repeatedly failed to keep pace with rising demand.
Last year, the Children's Commisioner warned that kids forced to wait years for autism diagnoses on the NHS are being 'robbed' of their childhoods.
Autism is not a disease and people have it from the moment they are born, although it may not be spotted until childhood and sometimes much later.
Autism exists on a spectrum. Some people will be able to lead fully functioning lives with no additional help. Others may need full-time assistance.
Meanwhile, NHS statistics show more than 230,000 people in England are now taking ADHD meds to combat their inattentiveness and hyperactivity.
Prescription rates jumped by a fifth last year, marking the biggest annual rise since modern records began in 2015.
Data suggests it has largely been fuelled by a rise in women in their 20s and 30s, although rates are still increasing in kids.
Experts have warned rogue private clinics are over-diagnosing the condition and have questioned the widespread prescribing of powerful stimulant drugs to treat it.
But others have also argued that ADHD was only officially listed in the UK as a disorder that affects adults in 2008.
Before then, it was just recognised as a childhood problem that kids grew out of.
As a result, rather than being over diagnosed, some experts claim many adults now being told they have ADHD have gone years having their symptoms dismissed.
Read more- Are skyrocketing ADHD diagnoses and a surge in super-potent medications threatening England's public health, despite controversial claims of over-diagnosis and mass-prescribing?
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