Additionally, do we know whether autistic people drink more diet soda than others? If autism is at least partly genetic, as it seems to be, then the mothers in the study might themselves be autistic or carriers of autism-linked genetic mutations.
I have read in prior research that overweight mothers are more likely to have autistic children. Another possibility is that being overweight is associated with frequent diet soda consumption, and it’s the mother being overweight that is more the issue than the soda consumption per se.
Anyway, I am not at all convinced of the implication that a mother drinking diet soda increases her child’s risk of autism, especially if the mother is at a healthy weight.