Your post confused me because you seemed to be comparing apples to oranges...saying abortion is natural because it happens in animals, when most people are opposed to abortion for a completely different reason-one that is not applicable to animals. It seemed like you were pointing out a discrepancy where there was none.
That said, if it's suffering you want to address, why use this particular example? I'm not sure preventing a recently fertilized embryo from implanting in the womb is really going to cause all that much suffering to mother or embryo.
Perhaps being clearer in the original post would have gotten the point across better and provoked the discussion you actually wanted.