Why do people choose to abort babies with disabilities?

The Word disabilities can be used very casual but the reasons when you are allowed to abort on those grounds are usually quite severe (when they find out late) and would mean a short, very limited or painful life for the child and the family might feel they can not care for a child like that. If the child would not be aware of what is going on around them and just be able to breath and swallow one can wonder what the quality of life is. Just surviving is not exactly a good life. It all depends on which disability you speak of of course.