We do not have sufficient knowledge of autism to make any sure statements, in my opinion. The "nerds mating" hypothesis would also explain a correlation of autism diagnoses with older mothers: the highly-educated mother (the bookish sort who didn't have boyfriends in high school) marries the socially-akward IT-guy whose economic value has suddenly skyrocketed. Is their child more likely to be autism-spectrum because of their genes? Is it her age? Is it her (physical) age or her (as it were) life-stage conditions? We don't know.
While there are many influencing factors, each of the above you mentioned influence the mother's ability to emotionally bond to the child. Bowlby and Ainsworth were more correct in their research than even they imagined.
I wonder if there is any correlation to the introduction of hormone based oral contraceptives and the “rise” in autism! The time lines for the rise in both oral contraceptives use and Autism certainly overlap. Lord that would cause an incredible amount of angst across the fruited plain wouldn’t it.
Seeing as how I’m a nerd/geek, I don’t like the “Nerds Mating” hypothesis! Thankfully, my kids turned out Ok. So I’ll toss out the contraceptive correlation as causation. ;)
We can generate hypotheses that “Make sense to me!” all day, without ever proving anything ... possibly without ever getting near the true cause or causes. Coming up with an idea is always the easiest part of science.