I am evolving towards a pro life stance as an atheist, because it seems to align more with reason, and if one is to be completely unemotional and pragmatic, abortion should be considered a last resort just like any form of violence against any life form.
Arguments I've heard from pro-choice folks are mainly from the "freedom over controlling one's own body" perspective.
Well, we all have the right to control our bodies but only to the extent it doesnt harm someone or in some cases some thing else.
As our knowledge of science expands, we see less and less distinction between humans and other life forms, and we've come to learn that all life forms have a common ancestor. This, to my way of thinking, makes anyone or anything capable of empathy accountable to the rest of the living things to be conscious of their fellow beings, and understand the gravity of responsibility when it comes to doing violence to another life form.
I dont know if this means either the extremes of no "morning after pill " or "abortions up to 1 second before birth", I dont like either extreme of the argument, as a rational, caring, loving human being.
I think the issue is more complex than pro life or pro choice as defined in our society, but I think as thinking, rational atheists, we need to acknowledge the complexity of the issue and , as we do in all scientific pursuits, constantly refine and re-evaluate our positions in light of new discoveries and be ready to put aside cherished beliefs in favor of doing the right thing.
For now, Id err on the side of caution. I cant imagine how incredibly horrible it would be to experience an abortion from a fetus's perspective. Thats something the pro-choice side is alarmingly quick to dismiss, stating that they feel no pain etc when we truly have no idea, and are pretty sure there is little to distinguish a third trimester fetus from a newborn baby.
My two cents.