This is the crux of the issue - which is the "greater" right, the fetus' right to life, or the woman's right to her body?
You argue by analogy, but I don't think your analogy is particularly relevant to the issue of abortion. Let's look at a better analogy. Let's say you were hooked up to someone with failing kidneys. For whatever reason (organ compatibility?), you were the only person that could be successfully hooked up the the patient. However, you had to essentially live in the room with the patient because if you were disconnected from the machine that hooked your kidney to his/her blood supply the patient would die. The question is, who has the greater right? The patient needs the use of your body to live. But your quality of life is reduced to the level of being a virtual prisoner. Is it ethical to allow the donor to say, hey, I want a better life, its not my fault this patient has bum kidneys, and I should be allowed to disconnect myself if I want?
This analogy has problems too, but its closer to the mark. And you can imagine better ones pretty easily in order to better get at the heart of the issue (maybe you only have to be hooked up to the patient for 9 months, for example). But it makes my main point. Even if you grant full personhood status to the fetus, it doesn't necessarily follow that abortion is wrong or immoral. There is a conflict of rights, but it is perfectly rational to conclude that the woman's right to her body supercedes the fetus' right to life (or that one person's right to life stops short when it imposes on other people's freedoms and rights).
Brett