Variation in hospital rates of induction of labour: a population-based record linkage study

Abstract

BACKGROUND: Understanding the extent of hospital heterogeneity in induction of labour (IOL) practices to identify areas of practice improvement may result in improved maternity outcomes. We examined inter-hospital variation in rates of IOL to identify potential targets to reduce high rates of practice variation. METHODS: Population-based record linkage study of all births of ≥24 weeks gestation in 72 hospitals in New South Wales, Australia, 2010-2011. Births were categorized into 10 mutually exclusive groups, derived from the Robson caesarean section (CS) classification. These groups were categorised by parity, plurality, fetal presentation, prior CS and gestational age. Multilevel logistic regression was used to examine variation in hospital IOL rates by the groups, adjusted for differences in casemix. RESULTS: The overall IOL rate was 26.7% (46,922 of 175,444 maternities were induced), ranging from 9.7%- 41.2% (interquartile range 21.8%- 29.8%) between hospitals. Nulliparous and multiparous women at 39-40 weeks gestation with a singleton cephalic birth were the greatest contributors to the overall IOL rate (23.5% and 20.2% of all IOL respectively), and had persisting high unexplained variation after adjustment for casemix (adjusted hospital IOL rates ranging from 11.8%- 44.9% and 7.1%- 40.5% respectively). In contrast, there was little variation in inter-hospital IOL rates among multiparous women with a singleton cephalic birth at ≥41 weeks gestation, women with singleton non-cephalic pregnancies, and women with multifetal pregnancies. CONCLUSION: Seven of the 10 groups showed high or moderate unexplained variation in inter-hospital IOL rates, most pronounced for women at 39-40 weeks gestation with a singleton cephalic birth. Outcomes associated with divergent practice require determination, which may guide strategies to reduce practice variation.