I do not believe that a fetus has absolutely any rights, at all. Since the concept of rights is based on man's nature, they're only given to fully formed and biologically independent beings. A fetus is a potential person whose very tangible existence depends on the direct physical nourishment of an individual, so ultimately the woman is left with the moral choice because she retains ownership of her own body.
The problem with that line of reasoning is that it can lead to atrocities such such as the Nazi
Aktion T4. (Can, not necessarily will.)
And the question to me isn't even about what is or what is not a human, specifically, since many things have human DNA but are not necessarily human.
Conversely for me, the question of abortion to me ultimately comes down to the question of what we mean by "human". If it is a human life, then the state has every obligation to act in a manner that allows for it achieve its full potential. If it is not a human life, then the state has no business interjecting itself in the decision. That is why I have no firm opinion as to when to draw the line between human and non-human, I firmly believe that the occurrence of rape or incest has no bearing on where to draw the line. Whether or not the biological father deserves to rot in jail has no bearing on whether a life is human or not.
(If pressed, I'd allow abortions before the fetus quickens, disallow them once the fetus is viable, and hope I'm never called on to give an opinion for the period in between.)