A friend posted this on facebook: http://www.bbc.co.uk/news/health-11071881
I suspect, first, that the study was looking at medicated vs. unmedicated OB births, not with midwifes. And from my own experience I know that not all OBs know how to help an unmedicated mother protect her pelvic muscles.
I also know I've seen studies that say the exact opposite. Hm.