First things first: there is no PROVEN link between the use of acetaminophen during pregnancy and the development of autism in children.

That's a pretty weak statement, though, and the rather thin read that Jansenn and then Kenvue, the makers of Tylenol, rely upon to make their assertion that Tylenol use does not contribute to the development of autism. - David Strom

• Scientifically proven links in medicine are relatively rare--in fact, there is relatively little evidence that a lot of drugs do what they claim to do, with the difference in outcomes between placebos and beneficial outcomes being modest to nonexistent. 
• Some of the most commonly prescribed drugs, such a SSRIs, are FDA approved despite links with serious or even fatal side effects and relatively small benefits that are barely distinguishable from a placebo. 
• There are plenty of dangerous surgical procedures, such as many back surgeries, that are often performed and are usually unsuccessful...