A correspondent has kindly pressed me on whether we really would want to say that fetuses don't feel pain given that newborn's clearly evince pain-behavior. My earlier post was certainly unclear on the matter, so here's a second pass:
Its certainly the case that newborns and therefore late term fetuses experience pain in at least its sensory components (and probably in some of its other more complex affective and conative aspects as well --but this is an empirical matter). And, I agree that the fetus is connected to its body in a relevant way. In fact, its probably the case that, the fetus/newborn is more connected to its body in the experience of pain than an adult human is to hers, since it doesn't have the sense of self as something above our bodies that we seem to.
My only point (insofar as I have a clear opinion on the proper account --I meant the post to mostly bring out some of the hard issues involved) is that by lacking the higher order capacities that adult humans and even adult housecats do, fetal/newborn pain has a different normative significance than adult human and housecat pain. The extreme version of this claim (which I probably myself don't endorse) is that a fetus being in pain is bad but not bad in a way that is bad for the fetus --its a hard distinction, its roughly the same point as the claim that the fetus feels pain but doesn't suffer.
Now, if this is coherent, inflicting pain upon fetuses is still bad and therefore ought to be avoided. (and presumably this is easy to do via opiates --indeed, from some of the literature on anesthesia during surgery on newborns it seems that low-dose opiates are safe in newborns-- and I suppose safety for the fetus isn't so much a concern in an abortion). What it does deny is the presumption that if the fetus feels pain it ought to be due certain legal protections in virtue of the pain being evidence for the fetus's moral status as a person (though that might be established on other grounds). Since that's the context in which the question of fetal pain usually gets raised, in the post I suggested that the proper (short) answer to the judge's question is no.
In any event, while I've thought a lot about pain and value in general, I haven't thought too much about the specific question of fetal pain (its going to be a section in a later chapter of my dissertation which I haven't yet begun), so its entirely possible that I'm all wrong about this. Still, the topic is hard and interesting; I'll greatly appreciate any further comments.