A grisly but apt analogy
Jill at Feministe makes a case against the anti-choice argument by invoking an unusual analogy: a baby born with two heads.
I watched a documentary the other night on TLC on an Egyptian baby born with two heads ... the baby was born perfectly normal — except that at the top of its head, there was another head attached. The second head only had a neck, no body, and it used the other baby’s body for all of its basic life functions. But it had its own brain. It cried on its own, moved its own mouth, and blinked its eyes. It was, without a doubt, a separate being — except that it was a parasitic head, unable to survive without the other head and body it was attached to. What did the doctors do? They detached it, without a second ethical thought...This is exactly right. Much of the abortion debate is spent on the alleged personhood of the fetus, but the fact is that this has little bearing on the matter. Even if we were to grant a fetus full personhood - an absurd proposition anyway - it would by no means follow that a pregnant woman is morally obligated to allow the fetus to inhabit her body.
...what this documentary made clear is that there is no moral or ethical responsibility for one being to allow another to live off of it. Is a parasitic head exactly the same thing as pregnancy? Of course not ... But the ethical issues of detaching this being that has no chance of survival without the body its attached to are certainly similar. Even if we argue that fetuses are entirely separate beings, why should women be required to carry those beings to term, and to allow them to live off of their bodies without their consent? How would this be considered fair, ethical or moral in any other area of medicine or law?