Well, it is killing a developing human, which, without an abortion, would become (minus complications of course) a human baby. The heart starts beating before 12 weeks, which the standard cut-off for legal termination, and the limbs are formed as well.
I'm against criminalizing abortion simply because it won't work. You can't (or shouldn't) force women to carry a pregnancy to term against their will. Sex education, contraception, adoption -- these are the methods that will reduce (and apparently have reduced) abortion rates.
But this notion, coming mostly from the men, I notice, that abortion is this ho-hum procedure (like having a hangnail removed)is seriously misguided. Most of the women I know who've had one are emotionally conflicted about it, and in certain cases there is extreme regret and guilt.
DP