I don't think this topic is an argument you can "logic" your way to a victory. You either feel a woman should have a choice whether or not she carries a pregnancy to full term, or you don't think she should have a choice.
Why would you want a woman to be forced to have a pregnancy, and thus a child, she doesn't want or doesn't feel she's prepared for though? What if she has a lifestyle that will be harmful to the unborn child (drinks, smokes, drives drunk, does drugs, gets in fights, etc.) and doesn't plan on changing that just because she's pregnant and doesn't want to be? Does society really need MORE unwanted births, and especially ones that have a decent chance of being born a burden upon society?
Maybe it's sad to think that "babies" are being killed, and that's emotionally taxing to consider, but emotions aren't a strong base from which to make decisions on things that have the potential to impact society (in a negative way) so greatly.