Ah, abortion. Always a fun argument because even after you eliminate religion, it is still an incredibly complicated scientific and ethical debate.

Just a disclaimer, all of my arguments run on the secular idea that no soul exists.

A personal solution I offer to this problem is incomplete yet I believe it is more complete than any other theory:
Humans are separated from the other animals on Earth mainly by the existence of an intelligent conscience. I believe this separation should distinguish when an abortion is legal. Up until the presence of a conscience (the start of brain activity to be more accurate) abortion should be legal. This allows plenty of time for drunk 16 year olds and raped mothers to correct the course if they wish.

The most prominent argument against this would be the mere existence of handicapped people. How do you define intelligent? I think there needs to be a standard, such as the existence of basic emotion and response to stimuli. If they pass the test (which 100% of current handicapped people would be able to), great!

Finally, the religious right, in their final death throes, would argue that apes and dolphins too have emotions and a conscience. Since us evil evolutionists think the crazy idea that we came from these apes and dolphins (?) we must put them on the same level as us.

Know what I would say? Fuck you.