There is a basic contradiction involved in permitting abortion while at the same time prohibiting prenatal harm. (1) This contradiction can be stated in personhood terms and in terms of the woman's rights. I'd like to elucidate that contradiction and examine three solutions which rise out of current literature; I'd like then to propose a somewhat new, fourth solution.
Stated in terms of personhood, the contradiction is this: abortion is permitted or condoned because the fetus (2) is not a person, but prenatal harm is prohibited or condemned because the fetus is a person. (3) Obviously one can't have it both ways — either the fetus is or is not a person.
Stated in terms of the woman's rights, the contradiction is this: abortion is permitted or condoned because the woman has the right to control her own body, (4) but prenatal harm is prohibited or condemned because the woman doesn't have the right to control her own body. Again, one can't have it both ways — either the woman does or does not have the right to control her own body.
1. The 'Other Grounds' Solution
One solution to the personhood version of the contradiction is to argue for the permissibility of abortion on grounds other than personhood. Arguments to personhood are usually a subset of arguments to rights: one argues for personhood in order to argue for the right to life. Eliminating this intermediary step and focusing directly on rights — and then not necessarily only on the right to life — provides such other grounds. When rights conflict, it is sometimes permissible to kill persons, most notably in cases of self-defence. Thus, granting personhood to the fetus need not preclude permitting abortion. (Alternatively, not granting personhood does not necessarily entail permitting abortion: the fetus may not be a person but may still have certain rights, not the least of which may be the right not to be killed.) Both Thomson (5) and English (6) develop such arguments for (and against) abortion which are rights-based and independent of personhood.
One can also argue against prenatal harm on grounds other than personhood. The fetus may not be a person and still it may be unacceptable to cause it harm; the arguments of animal rights advocates such as Regan (7) and Singer (8) may be applicable in this case. (Alternatively, the fetus may be a person and still it may be acceptable to cause it harm; surgeons do this every day. (9) )
The woman's rights version of the contradiction can also be solved by appeals to other grounds. There are grounds other than the right to control one's body that justify abortion. For example, abortion could be permitted because the fetus is not developing 'correctly' and/or its development and birth will likely kill the woman.
And prenatal harm can be prohibited even if one does have the right to control one's body. After all, non-pregnant women presumably with the right to control their bodies are not permitted to cause...