Is it wrong to have a vasectomy to keep from having another autistic child?

I always wanted a lot of kids, but my first born is a little flaky, then my second born is moderately autistic. He is very belligerent and very hard to manage, and basically makes all those moments that are supposed to be special our own version of hell. After we learned he was autistic, I got a vasectomy, because neither of us could take having more autism in our lives, and doctors say that after you have one, the chances are much higher of having another autistic child. I hate having a vasectomy, and feel less because of it, but I also feel like I had no choice in the matter. My wife and I agreed that one more child would be so stressful that It would literally be hell. I chose vasectomy because it is the 'easiest' of the sterilizations. I just wonder how many of you think this is a legitimate reason for a 33 year man who plans on staying married to get sterilized. It just sucks to know that all you can make is dysfunction when countless others go on spawning perfectly normal children with no thought in the world about it!