fetus' don't have any rights. a person who is BORN in america get's granted the rights of citizenship. an unborn person is not entitled to representation under the US constitution.
being that a baby is up to a certain point not capale of functioning indepedently of the mother's biological system, it's quite obvious to science and biology (ya know real stuff, not just people making shit up) that it is part of her body. So the whole debate is and has always been that women don't like the idea of men in particular telling them what they can and can't do with thier bodies.
and if you do want to argue biological ethiics as social convention, then you better be an anti-war, anti-death penalty, pro-welfare, pro-UNICEF, vegan.