I guess to elaborate a bit: The non-identity problem means that even choices that intuitively seem very morally dire when it comes to the kind of life you give your child can turn out to be morally neutral if the choice simultaneously changes the identity of the child you bring into existence. Because the results of biting the bullet on this seem so absurd to so many people, most papers in reproductive ethics kind of treat all choices about which child you bring into existence as though they are instead choices being made for the life of a single child. The reasons given vary a good deal, and there is more consensus that this is how you ought to treat these cases than why.
I guess to elaborate a bit: The non-identity problem means that even choices that intuitively seem very morally dire when it comes to the kind of life you give your child can turn out to be morally neutral if the choice simultaneously changes the identity of the child you bring into existence. Because the results of biting the bullet on this seem so absurd to so many people, most papers in reproductive ethics kind of treat all choices about which child you bring into existence as though they are instead choices being made for the life of a single child. The reasons given vary a good deal, and there is more consensus that this is how you ought to treat these cases than why.