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.
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