Variation in hospital caesarean rates among nulliparae at term is unexplained and unrelated to maternal or neonatal outcome: a population based cohort study

Abstract

OBJECTIVE To explore variation in hospital caesarean rates for nulliparous women; determine whether casemix, labour and delivery, and hospital factors explain the variation and examine the association between hospital caesarean rates and outcomes. DESIGN Population-based cohort study. SETTING New South Wales, 2009-2010. POPULATION Nulliparous women with singleton cephalic live births at term. METHODS Random effects multilevel logistic regression models using linked hospital discharge and birth data. MAIN OUTCOME MEASURES Prelabour, and intrapartum caesarean rates following spontaneous labour or labour induction; maternal and neonatal severe morbidity rates. RESULTS Of 67,239 nulliparous women, 4,902 (7.3%) had prelabour caesareans, 39,049 (58.1%) had spontaneous labour and 23,288 (34.6%) had induction of labour. Overall, there were 18,875 (28.1%) caesareans, with labour inductions twice as likely to end in an intrapartum caesarean than spontaneous labour (34.0% versus 15.5%). Variation in caesarean rates for term nulliparae 3 After adjusting for casemix, labour and delivery, and hospital factors, the overall variation in caesarean rates decreased by 78% for prelabour caesareans; for intrapartum caesarean by 52% following spontaneous labour and by 9% following labour induction. However, adjusting for labour and delivery practices increased the unexplained variation in intrapartum caesareans. The rates of severe maternal and neonatal morbidity were not significantly different across caesarean rate quintile groups, except for women in spontaneous labour, where the hospitals in the lowest caesarean quintile had the lowest neonatal morbidity rate. CONCLUSIONS Differences in clinical practice were substantial contributors to variations in intrapartum caesarean rates. Strategies aiming at lowering the caesarean rate should not adversely affect maternal or neonatal outcome.