I'll answer that. The fetus is completely innocent and completely without control of his/her situation. While it is convenient to label the fetus as "not life", it most certainly is alive. The fetus is being held accountable for the actions of the mother.
The criminal on death row has made his/her choices, relinquished his/her control of his/her life, and is now accountable for his/her actions.
It's pretty clear to me. Oh, and... if my wife was pregnant and you hit her while driving drunk and she lost the baby... I'd be going for manslaughter for all I was worth.