Introduction US data reveal a Caesarean rate discrepancy between insured and uninsured patients, with the C-section rate highest among the privately insured. The data have prompted concern that financial incentives associated with insurance status might influence American physicians' decisions to perform Caesarean deliveries.

Objective To determine whether differences in medical risk factors account for the apparent Caesarean rate discrepancy between Medicaid and privately insured patients in Michigan, USA.

Method A retrospective review was performed of 617 269 live birth deliveries in Michigan hospitals during 2004–8. All live birth records that were able to be linked to their mothers' hospital discharge records were utilised. Diagnosis-related group codes from the hospitalisation records were used to identify Caesarean deliveries. Regression models determined Caesarean probability for the time period under study, adjusted for insurance type, maternal age, race, maternal medical conditions, multiple births, prematurity and birth weight.

Results From 2004 to 2008, Caesarean rates were 33% for privately insured patients and 29% for Medicaid patients. The probability of Caesarean delivery was significantly greater for privately insured than Medicaid patients on univariate analysis (OR 1.2, 95% CI 1.19 to 1.22) but not on multivariate analysis (adjusted OR 1.01, 95% CI 0.99 to 1.02).

Conclusion No significant disparity was found in the odds of Caesarean delivery between privately insured and Medicaid patients in Michigan after adjusting for other Caesarean risk factors. A positive disparity would have provided de facto evidence that financial incentives play a role in physician decision-making regarding Caesarean delivery.