Here is a fairly close rendering of Alexander Pruss's brilliantly simple argument against abortion put in the first person. (I accept full responsibility for any errors, and part of what I say might go slightly beyond what Pruss says in the particular article to which I linked).
Let L name the living organism that came into being as a result of the sperm from my father fertilizing the ovum of my mother nine-months before I was born.
(11) Thus, there would have been no sufficient reasons which justified killing the fetus in the womb (from 9,10).**
*This allows for at least materialism about animals as well as hylomorphism. It's hard to see how it fits with substance dualism wherein I am identical with an immaterial soul. But then for those who think that they are identical to an immaterial soul, the best move might be to go with Idealism; and Idealism fits much better with religious monotheism than it does with naturalism.
**Pruss's argument does not explicitly go so far as to say that there are no justifiable reasons for abortion. His argument is focused on the fact that if one killed the fetus one would be killing my mother's fetus, that is, one would be killing me.