Costing the cascade: estimating the cost of increased obstetric intervention in childbirth using population data.

OBJECTIVE: To estimate the cost of "the cascade" of obstetric interventions introduced during labour for low risk women.
DESIGN: A cost formula derived from population data.
SETTING: New South Wales, Australia. POPULATION: All 171,157 women having a live baby during 1996 and 1997.
METHODS: Four groups of interventions that occur during labour were identified. A cost model was constructed using the known age-adjusted rates for low risk women having one of three birth outcomes following these pre-specified interventions. Costs were based on statewide averages for the cost of labour and birth in hospital. MAIN OUTCOME MEASURES: The outcome measure is an "average cost unit per woman" for low risk women, predicted by the level of intervention during labour. Obstetric care is classified as either private obstetric care in a private or public hospital, or routine public hospital care.
RESULTS: The relative cost of birth increased by up to 50% for low risk primiparous women and up to 36% for low risk multiparous women as labour interventions accumulated. An epidural was associated with a sharp increase in cost of up to 32% for some primiparous low risk women, and up to 36% for some multiparous low risk women. Private obstetric care increased the overall relative cost by 9% for primiparous low risk women and 4% for multiparous low risk women.
CONCLUSIONS: The initiation of a cascade of obstetric interventions during labour for low risk women is costly to the health system. Private obstetric care adds further to the cost of care for low risk women.