That assumes ones children will certainly suffer. And while some discomfort may be inevitable my experience is that many parents do consider the potential quality of life.

Often consideration is both for their children and themselves. My friends and I certainly thought about it and discussed such things.

Anyway, while children may experience good and bad things they'll also be free to decide if life is something they want to personally continue living or not. Many will also be free to choose whether or not to bring children into the world themselves.