A fertilized egg will, in the natural course of events, without any intervention by an outside force, grow to live a human life until it dies. A sperm cell will not. I've noticed this a lot in atheist people. To them, the future simply does not exist, only the present is real. We, on the other hand, are looking at the fetus not only as it is now, but as it is at all points in time along our current natural timeline. We see what it will be, and factor that in as a part of what it is.
A human being exists in many forms throughout its life. It is a human being in all of those forms. The same being inside your uterus will one day be running a jiffy lube. It's the same person. If you kill the fetus, you're killing the jiffy lube guy, they're the same person at different points in his life.
This is why life begins at conception. That is the fundamental point of human action where the timeline changes and an actual being forms that will live in a natural course of events.
Maybe they were Hitler in a past life and they deserve 30-40 years of hell on earth.