The biggest argument I have heard is that the human is TOTALLY DEPENDENT on the mother for survival. I then ask if any of the people with this view are parents. One or two will admit to this. I then request that they leave cereal, milk, fresh nappies and some clean water in a room with their 2-month old, lock that door and come back in 4 days to see what they find. The point is immediate.
Unlike other animals, God made humans to have a long period of post-gestational learning to absorb before we can function independently. Thus, their point is totally specious. Baby horses don't have this deficit; they can run in a week. As such, human babies are totally dependent on their parents for years as anybody with children knows fully well.
And if there could ever be a valid excuse for abortion, this is NOT it. It is the most ignorant thing to even put breathe into. The fact is, there is no valid excuse for any abortion. It's all just a lot of "who shot John".
Yep, it's amazing just how specious the arguments of the pro-aborts are, but they still cling to them ferociously.