Is autism hereditary? Scared for future kids

I haven’t told my fiancee yet but I’m actually scared for our future kids’ mental health. It’s not that I’m being paranoid or something. I’m just a bit worried. We’re not pregnant yet. We’re just about to get married after meeting each other 2 years ago in a foreign dating event. I just like to think about the future ahead of time.

She has a nephew and niece with autism. I think it runs in their family. While I don’t have a problem with that, I still would want to know so I could prepare everything, myself included, for such condition. Not everyone would understand the struggles of people with psychological problems. The least I could do is to prepare everything, i.e. finances, for their special education, speech therapy or other therapy, patience, etc so my future child would have a good life