From that link;
”However, genetics is not entirely responsible for a child’s chances of having autism. Environmental factors also contribute to the condition — although researchers disagree on the relative contributions of genes and environment. Some environmental influences, such as exposure to a maternal immune response in the womb or complications during birth, may work with genetic factors to produce autism or intensify its traits.”
Its not claiming to be definitive, even on that summary.
Click through further on the hyperlink of “although researchers disagree….” and the next article descibes two major studies, the competing theories that either 80% or 90% of the cause(s) of autism are genetic in nature, and some highly speculative ideas about what might be relevant “environmental factors” (such as flu).
It then goes on to say that there is clearly not one autism gene, and at least 100 genes closely associated with autism have been identified.
So essentially, it remains to be settled, but the genetics are highly influential, complex and not well understood. Some theories exist about epigenetics, birth experiences being a minor factor, but nobody knows.
Not exactly a slam dunk is it?
The incessant use of the word “risk” is grating, though.