Remember the study that said autism and ADHD are linked to acetaminophen use during pregnancy? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9385573/ Well it turns out that "Acetaminophen during bacterial colonization of the naïve gut is associated with lasting alterations in childhood microbiome composition": https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9367926/
I'm not saying these things don't have an influence on severity or presentation of ASD. But they are certainly not the root cause(s).