Pregnant people are physically restrained to the task at hand: hosting an embryo or fetus within their body. The pregnant person is physically forced to provide for the fetus literally from their own body functions. If the states extend personhood to the fetus and forbids breaking the physical retraints via termination of pregnancy, then it qualifies as both involuntary servitude and compulsory service--forced labor for the benefit of another person. Since there is no contract requiring completion of the pregnancy, then it must be considered to be an -at-will arrangement. When you remove the at-will aspect, it becomes compulsory service, aka, slavery. (as defined as one of the badges and incidents of slavery by the courts.)
I actually think you may be on to something with the 13th Amendment, but I'll get to that later.
Right now, I want to go over the fact that you're basically playing semantics games, not to mention committing several fallacies, but I'll go with your own argument since I can still offer a rebuttal for it anyways.
Although you're attacking a strawman, given that you're portraying personhood as something that's granted or denied by the state rather than what it's inherently about - a human being, either way, in a pregnant woman (and we know that it's a human being since it's the same species as the pregnant mother that it's in) & it's a question of human beings having a right to live, we can also discuss the issue of personhood for a pregnant mother and personhood for an Antebellum era slaves (as in Africans brought to the Americas as slaves and their descendants who were born into slavery).
Antebellum era slaves, based on your own reasoning approach or rules, had their personhood denied or taken away from them, as slaves brought to the Americas. In the same manner, an embryo or fetus of a pregnant woman is also having her or his personhood denied or taken away.
Note that you're explicitly assuming personhood for the pregnant mother by referring to her as a "pregnant person"; whether it's because you think it's inherent, or because you think it was granted once the mother was herself born, probably from - as you put it, a "forced birth", but you make no effort to defend why or how it's inherent or why it ought to be granted.
You want it to be inherent or granted that a pregnant woman is a person (and I wonder if you're using circular reasoning to come up with this conclusion), but you don't want it to be inherent or granted that an embryo or fetus is a person; that's a double standard. Which is it, do we have a contract to recognize human beings as people, or not?
If personhood is inherent (as opposed to something that's granted or denied to human beings by the state), then a pregnant mother is a person, an embryo or fetus in a pregnant mother is a person, and an Antebellum era slave is a person.
If personhood is just something granted or denied by the state, then that's not the test; the test is whether a pregnant human mother is a human being, an embryo or fetus in a pregnant human mother is a human being, and an Antebellum era slave is a human being; they're all human beings.
I'm actually with you that there has to be agreement about issues, policies, etc. That's exactly what the US Constitution in general is about; there are those who want to trash the US Constitution (such as with freedom from religion and right to keep and bear arms), and I'm very opposed to that (particularly with those 2 examples), but there can't be an agreement when there are any inconsistencies or double standards involved.
The inability of having an agreement with any inconsistencies or double standards involved doesn't have to do with someone's will or unwillingness to go along with the agreement or constitution; it has to do with being a logically impossible issue.
As I said at the beginning, I actually think that you might be on to something with the 13th Amendment and associating some laws regarding what someone can do with their body, but I don't agree with the approach you're taking to make your argument.
I used to be one of these rather absolutist pro life types, but have since changed my position about certain aspects of it. I still consider invasive procedures that involve ripping up a fetus to be manslaughter (I'm not an anarchist), but as a libertarian, I think someone has just as much a right to consume something that induces a miscarriage as they do to consume food, water, etc.
This means that I think that any laws that restrict or prohibit a pregnant woman from consuming something that happens to induce a miscarriage can be construed as a form of slavery, thus unconstitutional infringement of the 13th Amendment.
