Interesting thing I learned today is that if you want to do a natural birth (non-induced, non-c section, non-epidural, etc), stay away from the private medical system.
In the US, doctors generally work in teams, so if your birth takes 20 hours, then you might have a different doctor for the birth than your usual one. Usually they try to introduce you to the other doctors in the practice during the pregnancy so that the doctor doing the birth isn't a complete stranger.
Here, private doctors don't work in teams, so unless the doctor wants to stick around for 20 hours (unlikely), it's going to be wham-bam thank you ma'am, slap the baby on the butt and I'm out of here. The Spanish populace has been trained to think that this is a good thing, since it allows you to schedule your birth, make sure the grandparents are taking care of the kids, etc.
The other problem is that doctors in the private system in Spain sometimes have an inferiority complex (the really good doctors passed the exams for the public system, and do private work on the side), and thus can be extremely arrogant. Mention the public system and you are liable to get a half hour lecture on how crappy it is and how all their equipment is inferior, etc.
The real believers (mostly Germans here it seems) in natural birth do it at home, which seems a bit risky to me.
Anyway, you've been warned.