It's all a continuum. Nobody who understands the process that's involved really believes that life begins at conception. As others have pointed out, there are plenty of spontaneous abortions following conception--and nobody's holding funerals.
Anti-abortion zealots point to the fact that the fetus has a beating heart. Well, so what? So does an ant--and some of them have stepped on ants without a second thought.
If one defines a human life as when the fetus becomes viable, well, that's a start toward a rational definition. Butt what means "viable?" With huge machines and expensive round-the-clock care, medical technology is redefining viability all the time. Five-month fetuses can be considered "viable"...sort of. It helps that they've essentially designed womb-mimicking machines.
I love people who proclaim themselves "Pro-life." Most of them are very much in favor of war and the death penalty. That means that they're "pro-life" when it suits them. Isn't *that* "hypocrisy at its worst?" Later.