Our twins were in the same amniotic sac, so we had to choose when to start monitoring them daily to make sure they were not having decels leading to death from cord compression.
We did a lot of research into the matter, talked to a bunch of neonatologists at our local hospitals, and read several preemie baby books. We chose not to start monitoring until 26 weeks. I felt that if something happened before that time, sure we might be able to deliver the babies, but what state of life would we have chosen for them, you know?
I realize our situation is different because we had to choose while they were still perfectly fine inside, not while I was sitting in a hospital room in PTL.
That said, I think instead of an across the board determination of __ gestational weeks, there should be case by case decisions made with doctors and parents for every premature birth. While some people may be angered at not giving a 23 weeker a chance, other parents might be angered if there were drastic measures taken to preserve life because of the lifelong impact of doing such.
Just my two cents... my twins stayed in until 32W when we chose with our doctor to deliver them. We were in the NICU 5 weeks, but never had to deal with life threatening issues once they were delivered.