I think this situation is a little different and more complex than the examples you're comparing. I've worked in a NICU, and I've seen that many of the babies in it stay for several months at a time. Keeping these babies alive can be extremely expensive, and while considering costs in these situations is ugly, it is something that we have to do. Along with the costs, we have to consider the outcomes for these babies. We've only been able to keep babies born at ~20 weeks alive for a short time in medical history - we don't have a great idea about the long term outcome for them. We know that many of these babies are still alive, but we also know that many of them die very young from complications of pre-maturity like underdeveloped lungs, brain hemorrhage, necrosis of the GI tract, congenital heart defects, and sepsis.

The right thing to do isn't clear cut in this situation. Going to great lengths to save or prolong every baby's life isn't clearly a good thing, but neither is refusing care for premature babies.