Because of overcrowding, people reproduce by intermingling basic traits of their personalities into a young computer program. When the program has matured long enough it can be downloaded into a living body (which might not even be humanoid depending where in the solar system they live). Once in a living body, they are considered a person, regardless if they 'upload' again, but until that point the parents can choose to delete the program at any time.
I don't even remember if it was novel or short-story.
Thanks!