Sam2,
Pshat in the Rambam is the exact opposite. The whole point is that a baby can never be a Rodef during labor because that’s Tivo Shel Olam and Ain Dochin Nefesh Bifnei Nefesh. Thus, before Hotzi Rosho, the fetus isn’t a Nefesh.
That is not necessarily so. The Rambam does not state that a partially born baby is no longer a rodef. How could it not be, the mother is still in danger! It makes even more sense to me that when the baby is partially born, the mother herself can attain the status of rodef with respect to the baby – and in this case where they are pursuing each other, we cannot choose one over the other.
Also, I am enjoying the discussion of these points, but I don’t feel that they are fundamentally relevant to my point, unless you can tell me that there is a valid halachic opinion today that holds we can abort a fetus when the fetus is not at all a rodef (and yes, I understand that there are opinions that set the bar for rodef with respect to a fetus lower than others). Because that’s what the pro-choice camp holds.