The sad thing is you probably believe your position on this is some kind of proven science or even the more rational position, and it's simply not. Nobody is advocating slavery, but you very well may be advocating the destruction of human life, so I'll leave it to you to decide where you fall in the moral hierarchy. And let's not forget that so called "clump of cells" aren't just the woman's cells. Half the DNA is the man's, yet you demand eminent domain simply because it exists within your womb, which by logical extension must mean you also own the male part during intercourse and may do with it whatever you wish while it obviously counts as "your body".
By the way, when does "the last couple weeks of pregnancy" begin?