Idk, wouldn't signaling the decision to kill off your offspring be MUCH more difficult to handle rather than having them around, albeit in a difficult position?
I don't know; I think the decision to kill your offspring is simply inhuman.
Look; I work in a store. A couple times a week this middle-aged couple comes in with their teenaged daughter. She is severely mentally handicapped. She doesn't speak, she makes siren-sounds. Her movements are a bit awkward and her face has that particular genial blankness that accompanies a severe handicap. She prefers not to walk if she can spin around like a top. Sometimes she craps her pants.
But she always seems happy. She always smiles. She can't possibly ever life a normal life, and her parents are getting older. I don't know what happens to her when they are gone. I realize that's where you'd make the case for killing her.
But I see her, smiling, spinning around and wailing like a police car. There's a lot of things she's not, and will never be, but she is completely alive, and she seems pretty happy about it. And I think the way that other human beings treat her reflects the type of people that they are.
Or as Jesus said, basically, "what you have done unto the least of these, you have done unto me."
She's human, and she deserves to be treated like a human.