There are many excellent philosophical discussions of abortion, and many of these do tie the question to general moral issues. One classic article is Judith Jarvis Thomson's "A Defense of Abortion", Philosophy and Public Affairs 1 (1971), pp. 47--66. Thomson's argument begins, contrary to what public political discussion might lead one to expect, by granting that the fetus has all the rights of a person. She argues that abortion is nonetheless justified because it involves a conflict of rights.

Her central example goes like this. Suppose you were kidnapped by music lovers and connected via tubes and wires to a famous violinist whose life now depends upon your remaining connected to him. If you remove the tubes, he dies; if you remain connected for nine months, you both live. Do you have a moral duty not to remove the tubes? Thomson grants that it would be very nice of you not to do so, but, intuitively, you have no such moral duty. The example is meant to be analogous to cases of rape. Here's a variation that's no longer science fiction. Suppose a woman were kidnapped and, while she was asleep, embryos were implanted in her uterus. Does she have a moral duty to carry them to term? If you don't have such a duty in the case of the violinist, how does the woman have such a duty in this case?

To extend the argument beyond cases of rape, Thomson offers other examples. There are large questions about responsiblity that arise here. Many people think that, in cases that do not involve rape, the woman bears a certain responsibility for the life of the fetus that is morally relevant. It's not an unreasonable view that there is some moral difference between the cases. Whether it is enough of a difference to make abortion morally impermissible except in rape cases is another question.

Thomson's paper is collected in several different places, including in Joel Feinberg's collection The Problem of Abortion, where you will find some critical discussion.

A much cited, more recent paper is Don Marquis's "Why Abortion is Immoral", Journal of Philosophy 86 (1989), pp. 183--202. There are two replies in the May 1990 issue of the Journal of Philosophy. Walter Sinnot-Armstrong's paper "You Can't Lose What You Ain't Never Had", Philosophical Studies 96 (1999), pp. 59--72, seems to me a balanced discussion that ends up being critical.

Why hasn't the philosophical discussion had much effect on the public debate? I expect the reason is very simple: Abortion tends to generate strong emotions, and where there are strong emotions, reason stands little chance of a hearing.