Inspired by my own experience and talking to two friends who's children are autistic.
My DS, 8, diagnosed ASD (formerly Aspergers, geeky-intelligent type). I think comes from his father (my ex). Their ASD traits are very similar and I think his father would definitely be diagnosed. DS also has ADHD which I think comes from me (I have lots of traits) and this is his primary diagnosis and much more prominent. So in our case, I lean towards genetic, although I was anaemic during pregnancy, had a low lying placenta and DS was born via induction and ventouse.
I'm pregnant with DC2, this time a girl, and my current DP has no ASD traits, and none I can see from anyone in his family. I am, however, anaemic again and this time facing having an iron infusion as the tablets haven't worked. I've read some research that low iron in pregnancy can be a potential cause of autism.
My friend has a 3 children, only one (DS2) is diagnosed Autistic. He has a more classical presentation, non-verbal, developmentally delayed and requiring a special school. She feels his autism comes from a long and traumatic birth, and she has no family history of ASD.
Ditto for another friend, she also has 3 children, and her DS1 is both Autistic and has learning difficulties. Her other two children are unaffected. Similar to my first friend, she thinks the cause of his autism was a long and difficult labour and birth trauma. No family history of ASD, although I can see some ASD traits in her DH!
What do you think the cause, if any, in your personal family experience?