EDITOR, - The controversy over the optimal rate of caesarean section continues^1,2 in the absence of clear evidence on the relative benefit of higher or lower rates. There is a large literature on the variation in rates, but this is mostly concerned with its determinants^3,4 rather than the more fundamental question: what difference does it make?

Craig R Leitch and James J Walker state a commonly held view - that the focus of study should be the reasons or indications for caesarean section.2 Yet, as they also state on the basis of their unit's experience over 30 years, a large difference in caesarean section rates (7% rising to 17%, judging from their figure) is compatible with the absence of change in the most common indications, failure to progress and fetal distress. Both these indications are continuous variables, so it is …