I can't speak for anyone else, but it definitely wouldn't surprize me if it has something to do with our parents' health. I'm 99% convinced that in my case it's a problem of a lack of nutrients in my mother's body (and maybe my father's condition at the time of me being conceived helped). I was born very premature (at 28 weeks) and have a random genetic eye mutation that came with birth, that no one else in my family has, causing me to be almost blind. Recently I found out that a lack of vitamin A (I think it was) will cause a cow's calf to be born blind, and that each progressive generation of human mothers that grows up on bad nutrition (meaning: stuff like English/French/American food) has progressively more and more problems giving birth, among other things.
They thought I would be brain-damaged and have learning disabilities but that didn't happen. My mom couldn't stop bleeding after the surgery to get me out (which again points to some kind of deficiency) so they almost gave her a forced hystorectomy or something like that so that she wouldn't die, but she stopped in time.
Knowing all that I know now about nutrition, my mom's probably only getting like 5% of her daily nutrients and has been living like that for as long as I've been alive at the very least, ingesting poison (like aspartame) on the side. She's constantly sick, has tons of pain, can never sleep and so on because all she eats is junk food and I don't know how it was before I was born but I imagine it was similar. She also used to go to those tanning salons all the time, the kind that use radiation, and she never used to listen to me when I told her that this or that caused cancer or that this or that food was no good, so I really have no idea what she was up to before I was born. She takes a lot of pills, like antidepressants and anti-allergy pills, nowadays but I don't think she took anything when I was a kid.
If you want to be healthy and get all your nutrients you need to eat stuff like liver and soaked beans, and stop eating stuff like table sugar, white flour, microwaved food and ultra-pasteurized dairy products (by the way, if you hear stuff like "red meat causes cancer" - most meat nowadays has sugar in it, sugar causes cancer. Not sugar inside honey or fruit, I mean stuff like table sugar and molasses). My mom, for long as I can remember, has only eaten the cheapest food that has tons of sugar, white flour and artificial food colouring in it, stuff like instant macaroni and cheese in a box, with hamburger meat so cheap it's been filled out with so much who-knows-what until it's a different colour than it should be, topped up with McDonald's. If you're not even getting all of your OWN daily nutrients then it's no wonder if the kid you have is then born abnormal.
As for what medicine/drugs she may have taken, I have no clue, but she was born in the late 60's (me in the early 90's). She hardly drank, never got drunk, and never smoked - but her mom smoked cigarettes (and possibly marijuana) inside the house while she was growing up.
There's a lot of info out there now about how stuff like when children have a lack of nutrition or eat artificial food colourings, it cause stuff like ADHD and Asperger's symptoms. I would guess that some fetuses are just affected in different ways to the same stuff, so maybe you got Asperger's and I got ->-bleeped-<- and eye problems, you know?