Not saying it's not worth investigating or pursuing, but "autism" is a clinical word, like "psychosis" or "schizophrenia".. underlying mechanisms aren't always well understood and disorders that present similarly but have completely different origins get lumped under umbrella terms.

I'd say LLMab looks promising for prenatal prophylaxis of disorders arising from maternal immune (over)signaling, but this is one area medicine and science are often loathe to explore for very valid reasons. Would have to be some extremely compelling animal studies to even consider it. Not low hanging fruit at all.