I think there is nothing wrong with abortion as a form of contraception, except maybe the inconvenience.
My reasoning is that you are not terminating a sentient being. It strikes me as a fairly simple issue. People seem to get caught up on valuing the potentiality for human life. I don't consider the potential for human life (ie, a fetus) to be equal to a realized human life.
So, how to value a non-sentient fetus seems to be a crucial question to me.
The social valuation: given that the world is increasingly overpopulated and modern infant-survivability, I do not think there is an overwhelming social necessity to procreate. That is, society's demand for children is being met. Thus, I think (in the modernized world), it is time to move towards a "more eggs, less baskets" approach to child-rearing.
In summary:
* A financially anticipated, planned pregnancy to intentional parents == GOOD.
* An 'Oops' pregnancy == NOT GOOD.
Personal evaluation:
Our hypothetical woman obviously doesn't really care about the abortion. No harm there.
A more interesting hypothetical situation:
A man walks up to a pregnant woman and gut-punches her, causing a miscarriage. What is the appropriate legal recourse?
My answer:
The assault is clearly a simple matter to be resolved in criminal courts.
The miscarriage is more complicated. It strikes me as more of a civil matter. The expecting mother can legitimately seek reimbursement for the lost effort of her pregnancy, emotional damage, whatever. But I do not think the fetus represents a legitimate legal victim -- it would best be handled a work-in-progress kind of property.
(As an aside, I think the second murder charge levied against Scott Peterson was bullshit. Although, I have a hard time feeling bad for him.)
For how long can we safely say that a child is non-sentient?
Off the top of my head, I don't believe that a fetus' frontal lobe is properly "hooked up" until at least ~week 25. That seems like a good lower bound.
People like to construe reflex actions as proof of sentience, but I disagree with that. "Look, it moved when I prodded it, clearly it can feel pain and is alive." That simply does not follow; it indicates that some low level brain functionality is up and running. The parts of the brain responsible for that kind of behavior have been proven to develop much sooner than other (more important) parts, and sooner again than those parts begin to integrate.
Here's a very good paper on the subject (do a search for 'projection fibres'):
