I said earlier that the question of abortion is a question of when the fetus becomes a human with the rights inherent.
Now, my personal belief, is that happens sometime between first brain activity (at about 40 days) and viability (sometime around 21 weeks). Which means that, at the least, partial birth abortion and other late term abortion should be banned.
But let's say that you and I have equal evidence. Wouldn't we want to err on the side of caution? Going by your measure, if you're wrong, means about a million dead kids a year.