When I think of natural births, I think about nature. Think about it, how many mammals out there use pain relief such as epidurals, pethidene etc? How many animals are using tools to break their waters or pull their babies out? Or cut themselves open to remove their baby? Humans are the only ones to do these things.
Is it a bad thing? Not necessarily, because in nature if some of these necessary things haven't been done then the baby will pass away, as well as the mother.
ETA: I don't say the above to be offensive. I say it because thats what natural is, back to your animal instincts without any of the human technologies and evolutions to get in the way. Do I expect mothers to go find a cave and give birth as if they were animals in the wild? No way. I wouldn't do it, that's for sure.