system
Given the following post, respond as if you're commenting on Reddit:
human
Why shouldn't personhood start at conception?

Pro-lifers do not seem to care about the concept of "personhood" but rather just that human life is present.

Other than the example of abortion, where a persons bodily autonomy is removed in favor of a living human organism that is not a person, are there other problems that arise or ethical reasons why we shouldn't just take the religious approach and say that personhood starts at conception?
gpt
This paper might be worth reading for you:

Tooley, Michael, 1972, “Abortion and Infanticide”, Philosophy and Public Affairs, 2(1): 37–65.

But it’s also worth pointing out that the morality of abortion arguably doesn’t even depend on this point. The most influential defense of abortion is Thomson’s, and her argument grants it that fetuses are persons with a right to life, etc. and shows that nevertheless, abortion is permissible:

Thomson, Judith J., 1971, “A Defense of Abortion”, Philosophy and Public Affairs, 1(1): 47–66.

But see Tooley’s paper if you’re really interested in this particular question. (It sounds to me that you’re not terribly interested in abortion itself, but this issue is almost always treated in conjunction with abortion. Tooley’s paper is worth reading for the debate itself, even though he  does draw the connection with abortion.)