Life begins when life begins. Life can, in fact, be biologically dependent on another organism. Not a perfect analogy, but good enough to show that your definition of life is scientifically flawed. I remember how devestated I was when a couple that lives not far from here returned home from an evening out and found their 17 year old daughter dead on their living room sofa. She had tried to give herself an abortion with a vacuum cleaner.
Abortion is never safe.
It always has one victim, and in this case, two.