+mbs: here again I think you're a little pregnant, no pun +intended. Personhood connotes rights. And surely the most +basic right is to exist, which in and of itself trumps any +concern by the mother, other than equivalent biological +existence.
Couple of jumps in your logic there-- yes, (A) personhood does connote rights, but (B) "personhood" is not a simple binary trump card once you start extending degrees of personhood to animals, fetuses and so on. The problem is in the whole trump card approach to rights. I actually prefer to talk about values because that steps away from the absolutism that "rights talk" usually lands us in.
I believe in limited animal rights-- no cruelty and escalating protection based on sentience -- but I'm still a meat-eater and don't think that, because I oppose torture of animals for cosmetics research, I then have to extend the right to vote to chimpanzees.
Similarly, we can acknowledge that we value the potential life of a fetus-- god knows any parents rubbing the belly of their unborn child do -- without extending it a trump card to life that enslaves the mother to judicial dictates. "The right to life" is not absolute-- one has the right to self-defense to avoid kidnapping and slavery, and enslaving mothers for the benefit of unborn children does not clearly lose out even in a "trump card" approach to rights.
But I think the rights talk stuff just blurs the more complicated reality that fetuses and even small children are more potential life than fully equivalent humans, yet we extend them far more rights than chimpanzees which have higher intelligence and communication skills. There are a whole set of moral, political and strategic reasons why we do this that are not captured by simple binary trump card approaches to rights.
One reason I am opposed to Roe v. Wade philosophically is that it encourages this binary approach to rights and in many ways empowers the rhetoric of the "right to lifers" who just propose an alternative trump card to the right to privacy (always a rotten part of the decision, since a defense of women's right not to be enslaved either individually or socially as a group is far stronger in any case).
-- Nathan Newman