The public relies on measured, careful statements which are rooted in robust scientific research when deciding what medicines or vaccines they or their children should take.

When US president Donald Trump claimed on Monday in the Oval Office that taking Tylenol, known as paracetamol elsewhere, "is no good" and that pregnant women should "fight like hell" to only take it in cases of extreme fever, he delivered conjecture, personal opinion and gut feeling.

On paracetamol there is recent research - a review of studies - which suggests an association between paracetamol use in pregnancy and autism in children, but no causal link, meaning there is no strong evidence suggesting a risk.

Other researchers found no connection, but President Trump went much further in his comments, urging women not to take the medicine during pregnancy unless they couldn't "tough it out".

Health officials in the UK have stressed that paracetamol remains the safest painkiller available to pregnant women, but that it should be used at the lowest dose and for the shortest possible duration.

Aspirin or ibuprofen is not normally recommended because these drugs can affect the baby's circulation.