Unexplained variation in hospital caesarean section rates

In reply: We thank Fielke for his interest in our article.1 Our study used the 20th centile method of the Australasian clinical indicator report on obstetrics, conducted by the Australian Council on Healthcare Standards (ACHS).2 The ACHS defines the 20th centile as a “best practice rate” that is potentially achievable and uses it to identify and prioritise clinical areas in which research and quality improvement activity would have the greatest benefit. Using the 20th centile rate for quantifying the potential impact on the overall caesarean section (CS) rate of reducing practice variation is appealing, as it does not rely on an arbitrary target value but instead is data driven, being influenced by the rates currently achieved by 20% of hospitals. Importantly, appropriately risk-adjusted CS rates, rather than the observed rates, should be compared with the 20th centile.

However, we urge caution in immediate use of the 20th centile, as lower CS rates should not be achieved at the possible expense of increased adverse outcomes. Our initial study1 aimed to identify clinically relevant groups with the greatest (and potentially most modifiable) variation in hospital CS rates, adjusted for casemix. A detailed analysis of outcomes was beyond the scope of that study. We are currently exploring the Robson groups with the greatest variation in hospital CS rates using more comprehensive data obtained through record linkage. Our aim is to identify further factors contributing to variation in each group, if any, and to examine the relationship between CS rates and maternal and neonatal outcomes.