For whom is the Caesarean section rate high?

Aim. To define a method for examining and comparing Caesarean section rates . Methods. Data on Caesarean section rates at National Women's Hospital for 1 997 were analysed by two methods which adjust Caesarean section rates accor ding to casemix: 1. standard nulliparae and 2. grouping women by factors in fluencing Caesarean section rates. Results. The Caesarean section rate in New Zealand is rising and National W omen's Hospital had a Caesarean section rate of 22.3% in 1997. The instrume ntal vaginal delivery rate was 13.1%. Our 1997 data were analysed for casem ix - standard nulliparae and dividing women into six distinct groups. The C aesarean section rate for standard nulliparae was 19.2%. Nulliparae had an increased induction of labour rate compared to multiparae (29.1% versus 22. 9%, p < 0.001), The Caesarean section rate was increased in association wit h induction of labour for nulipare (26.0% versus 13.1%, p < 0.001), multipa rae with unscarred uteri (5.4% versus 2.5%, p < 0.001) and primiparae with previous caesareans (36.8% versus 30.4%, p = 0.02). Conclusion. We suggest our second method of grouping women by the most impo rtant factors influencing intervention rates should be used by obstetric un its for benchmarking and internal audit purposes.