Rules: no logical fallacies, no legal arguments, unless it pertains to ethical/moral reasoning.
My position: abortion is morally acceptable.
The principle of consideration of interests, which my position on abortion arises from, comes from the simple fact that as conscious beings with a certain brain capacity (that capacity being; we are conscious, self aware and are capable of thinking so as to hold interests) we hold and seek to fulfill certain interests.
We have no reason to consider our own interests anymore important than that of another simply because it is our own. Consequently we can say all interests should be considered, and considered equally. The implications of this principle in the abortion debate are rather straight forward. The interests involved, in the immediate circumstance are the mother and the fetus. The fact is however the fetus has no interests - let alone an interest in its existence. If it had preexisting interests, as say an unconscious (born and grown) person does, there would be grounds for reconsideration of abortion, but the fact is there aren't. The only interests to be considered are that of the mother. Killing a fetus does no harm to ANYONE because the fetus doesn't care if it lives or dies - it doesn't even (however you describe or conceptualize the mind) know, comprehend or think of its own material existence as an entity. It has no conception of space, time, of itself or of anything within the confines of reality. It has feelings in the most primitive sense of psychical sensations, sure, but that does not constitute an interest or evidence that the mind has developed to keep an interest in living. This emerges only after the first few weeks of being born - but never before.
Now, as indicated, this does not mean anyone can be killed, only those entities that do not have enough mental capacity to think, hold an interest and thus value their own existence.
Consequently my position is this:
Killing a fetus is fine because the baby has no interest in its own existence.
This means whether its human or not is COMPLETELY IRRELEVANT AND NOT A VALID ARGUMENT THAT WOULD REFUTE MY POSITION. The fetus is a human being, sure, but so what? Right to life is dependent on the holding of an interest - not being a human being.