HELP! Is this a good reason to be scared to have children?

I'm scared to have children because I'm afraid that they might end up with cerebal palsy or any other type of disease that can make them handicapped. I'm just so scared for some reason because I don't want to see my child or anybody else's child like that. None of those diseases run in my family however. The only big thing that runs in my family is diabetes. Do I have a reason to be worried??