If the child has 23 of the Man's chromosomes after birth, that child also has 23 of the Man's chromosomes before birth. It actually makes total common sense. No single person can create a child by themselves. The parents are equally the Man's and Woman's. So, as a Man, the child isn't yours till it comes out the womb?
legally speaking .. that answer (currently) is YES !!! The child isn't yours till it comes out the womb..
Morally and figuretively, the answer is NO.. that : ball of cells, fetus, premie is as much yours as the Woman you mated with. The grey area comes in the fact that the child is carried in the Woman's body.