Perhaps everyone's pain nerves are different in abundance or distribution. There are many ways pain can contribute to the general discomforts of labor and delivery. Each individual woman is unique in the way all of these causes of pain gang up on her. Natural childbirth techniques, generally successful, cannot always eliminate that one type of pain a woman may be most sensitive to. Let's be fair.
Natural childbirth is an ideal for a natural process.
But let's not forget that not too long ago dying in childbirth was a natural part of this also. Now I'm not saying that the pain of labor can cause death. The woman who feels she needs something will be the first to tell you her relief is not off-limits. As an obstetrician I can tell you that all I care about is getting a healthy baby and mother out of all this. There are certain guidelines expected of me to get to my goal, and as far as I'm concerned, the parents are the boss for everything else.