I have a disabled child as well, so I understand what you're saying.
But I have two comments - the first is that this screening question is not about abortion. It is a way to get at deeply held beliefs about whether women are capable about making decisions about their own bodies and lives.
The second is that I would never force someone (knowingly) into the life that you and I have ended up in. New treatments allowed my daughter to become a fully functioning adult, but when she was young I thought I would have to care for her until she died.
There are just as many parents who have emotionally checked out on their high needs child. Some learn from it and find meaning it. Some don't. So I stand by a woman's right to make that decision for herself.