Current evidence does not link paracetamol use in pregnancy to autism, experts have said after a new review of studies on the topic.
US President Donald Trump said in September there had been a "meteoric rise" in cases of autism and that Tylenol, which is called paracetamol in Ireland, was a potential cause.
He said the painkiller should not be taken during pregnancy, suggesting pregnant women should "tough it out".
His comments were criticised by autism campaigners and scientists.
Experts said they hoped the latest study would "bring the matter to a close".
Researchers conducted a wide-reaching review on the topic, which has been published in the journal The Lancet Obstetrics, Gynaecology and Women's Health.
An international team of academics searched research databases for all studies reporting risk estimates for autism, attention-deficit hyperactivity disorder (ADHD) and intellectual disabilities.
Studies deemed eligible for the review compared pregnancies with and without paracetamol-exposure, as well as looking at validated questionnaires or medical records on medical outcomes.
They also looked at other ailments mothers had and the other treatments they received.
Some 43 studies were included in a systematic review, an overarching review of the data, and 17 studies in the meta-analysis - a research method for systematically combining findings from multiple studies.
A number of so-called sibling comparison studies were also included.
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Paracetamol safe to use in pregnancy - European Medicines Agency
These studies compare children born to the same mother, where in one pregnancy the mother took paracetamol and another pregnancy, she did not take paracetamol.
The authors conclude that paracetamol exposure during pregnancy was "not associated with the risk" of autism spectrum disorder, ADHD or intellectual disabilities.
"Current evidence does not indicate a clinically important increase in the likelihood of autism spectrum disorder, ADHD, or intellectual disability in children of pregnant individuals who use paracetamol as directed, supporting existing recommendations on its safety," the authors wrote.
Study lead author, Professor Asma Khalil, consultant obstetrician and fetal medicine specialist at St George's Hospital, London, said: "We found no clinically important increase in the risk of autism, ADHD or intellectual disability (among) children where the mothers took paracetamol during pregnancy.
"And this is the important message to the millions of pregnant individuals, paracetamol is safe to use in pregnancy.
"It remains to be the first-line treatment that we would recommend if pregnant women have pain or fever in pregnancy, and it's also consistent with recommendations or the guidelines by various national or international bodies," she added.
Commenting on the study, Gráinne McAlonan, professor of translational neuroscience at King's College London (KCL), said: "Expectant mothers do not need the stress of questioning whether medicine most commonly used for a headache could have far-reaching effects on their child's health.
"This thorough and clear study approached the question by conducting both a substantial systematic review of the literature and a meta-analysis of eligible studies.
"Importantly, it prioritised sibling design studies to account for family history, which is crucial," she said.
"This confirmed that there is no relationship between taking paracetamol in pregnancy and a higher likelihood of autism, ADHD or intellectual disabilities in the offspring.
"While the impact of last year's announcement has been extensive, I hope the findings of this study bring the matter to a close," she added.
