The ethical question on abort can be compared to a heads up Texas Hold 'Em poker game. When you are small blind, or big blind and the other player has raised, you are considering wether you should call or fold. The flop about to come that could make your hand good or bad, can be thought of as both existing and non existing. It doesn't really exist because no one has seen it and the cards are random, so the potential hand you could get doesn't exist before the flop is shown, therefore you do not lose that potential hand if you fold, as it doesn't exist yet.
The same way when a baby is growing inside a belly it is only a potential person. It is only a certain set of genes and a biological animal, there is yet no soul. In my head what makes a person into the person he or she is, is the things that happen around and to him or her, and not the genes which merely is how a person is biologically build. So in that way a baby inside a belly does not exist before it is born.
So in the same way as the poker hand before the flop, one does not lose anything by giving it up.