There is a correlation between mothers who take tylenol while pregnant and children who develop autism in some studies.

All people with autism, also had mothers who consumed water during their pregnancy... Did water cause autism?

But it could be just as likely that autism is both hereditary

At this point, it's almost a certainty that this is the case, possibly activated by environmental influences during pregnancy. However, none of the influences have been identified, as there's (Last I looked) about 30 separate DNA sequences that are related to autism in people.

For what it's worth... there's about the same number of DNA sequences involved in someone requiring corrective lenses.