@JenniferP the funny thing is that the Bible, the book that pro-life people seem to like so much, presents us with the exact scenario which you describe.
When people who are fighting injure a pregnant woman so that there is a miscarriage, and yet no further harm follows, the one responsible shall be fined what the woman’s husband demands, paying as much as the judges determine. If any harm follows, then you shall give life for life, eye for eye, tooth for tooth, hand for hand, foot for foot, burn for burn, wound for wound, stripe for stripe. —Exodus 21:22
So according to the Bible, killing a fetus is just punishable by a fine, whereas if the fetus’ mother is killed or even harmed it’s eye-for-an-eye. Apparently ol’ Yahweh himself does not believe that killing a fetus is equivalent to murdering a person.