Interesting that someone mentioned Northwick Park. I gave birth there - went into labour three days too early to go to the MLU I'd planned to.
It's a horrendous, scary shithole but I was lucky to be there just after they had been put into special measures and I had very good MW care. I see from the papers, however, that three more women have died there since I gave birth there.
Let me try and explain what I mean about 'positive experiences' now I've calmed down a bit.
The problem with the 'positive attitude' thing is this: your labour, really, has nothing to do with your attitude.
You could have the most positive attitude in the world, ever, and you still might have to have intervention to save your life and that of your baby's.
What happens in your labour is down to sheer, blind luck. But many women are not told this. They are told that if they have a positive attitude, they'll get through it fine. They vaguely know about interventions, but hey, that won't happen to them - they have a positive attitude.
Hence, when they are faced with the realities of birth, they are utterly terrified. If they go for intervention - even when it's necessary - they still feel that they've failed.
Here is some interesting research about women's expectations of birth. Women saying they had no idea about the type of pain, how long the pain would last, what they could do about the pain.
www.biomedcentral.com/1741-7015/6/8
If I had to tell women to have any kind of attitude about birth, I would recommend 'prepared' rather than 'positive'.