I came across this a little while ago - skepticalob.blogspot.com/2009/07/whats-safest-c-section-rate-higher-than.html
The blogger won't be to everyone's tastes, but it's the only piece of critical analysis I've seen of the WHO's much quoted CS target of 10-15%.
It's interesting that they say now there is 'no empirical evidence' for such a limit.
I also found out today that (a) the WHO recommended 'target' of 10-15% was actually issued in 1985, which is a lot longer ago than I had imagined. And (b) it seems the WHO retracted this recommendation last year! - www.medicalnewstoday.com/articles/169058.php
In which case it seems remarkably under-reported.