My husband's brother is autistic. How big is our chance of getting a child with autism?

Good question. I understand your concern. My understanding is that given the range of ''autism'', first is there other instances on your husband's side. (i suspect not, think you would have included that). Let's start with probably little. Now, please consult with your gynecologist for his opinion and that of a geneticist. But, still no guarantee. I believe chance will be on your side. Take care.