(my thanks to Yulia Massino for calling my attention to this video; for some reason I cannot create a link here). Welch is carrying out a research project on the effectiveness of Family Nurture Intervention as a prevention of autism and has described the research plan, a randomized controlled trial, at https://bmcpediatr.biomedcentral.com/articles/10.1186/1471-2431-12-14. Among other things, Welch proposes that autism is related to the presence of abnormal levels of peptides released from the gut, for example secretin and oxytocin (both popular suggestions for treatment of autism in CAM circles).
N.B. Nothing in this post should be taken as rejection of the extensive legitimate research on neural factors in gastric and endocrine functioning; my point is that the existence of such physiological factors is not in itself evidence that supports any statement about autism.