My husband's mother's father's side of the family has a lot of autistic traits and from what I've heard from my in-laws, it goes back quite a ways. Had my husband been in elementary school now, instead of in the seventies, I'd bet money he would have had an IEP for being on the spectrum.
Add to that, my being pretty introverted and having quite a few HSP traits . . . It just isn't that surprising.
Our daughters are considered neuro-typical. Our sons didn't have more than a few words until they were four, had major sleep problems (have it under control now thanks to melatonin supplements), had toilet training difficulties, they have some sensory issues (don't like loud noise, picky eaters, vertigo with high ceilings, etc), problems with obsessing/persisting and being impossible to distract/comfort.
We have to make allowances for food and be aware of high ceilings, and handle loud noise problems. Yesterday for example, we visited my mom's church which has a contemporary worship service, so my son kept his hands over his ears until his arms got tired, then I put my hands over his ears until my arms got tired, then he took back over.
I have to make sure the school works with them, but I don't have too much trouble with it now. Overall, it isn't much of a big deal. All kids have stuff you have to deal with. Mine have better analytical skills than a lot of kids their age and I really don't deal with a lot of sassiness or violence, etc with them.
I think the cause of the increase in people with autism is a combination of nerd genetics and better diagnosis. I also think we're still at the beginning of learning about autism and eventually there will be more specific diagnoses and more proven and effective treatments. Probably also some pre-natal screening tools, as well, which I have mixed feelings about.
I don't really think it was preventable for my husband and I to have kids on the spectrum -- outside of just a different roll of the dice. I am open to the idea that there are environmental factors, but I don't believe we've found them yet, if there are.
What we know right now is that early diagnosis and intervention can help most kids make some improvements. I think early intervention, behavioral treatments, family support, and public awareness are a good place to spend resources until science and medicine catch up.