Is it normal to have these thoughts?

I keep seeing news stories about autistic kids or kids with cancer or other diseases that have to go through so much pain and suffering to get through it. I keep realizing that even if they make it through, there's no way they can live a normal life, or contribute to modern society. I feel like a terrible person for thinking this way but... why do we let them procreate and damage our gene-pool? we can't afford to have weak or sick people in society.If they can't contribute, it can't be everyone else's responsibility to carry their weight as as well.