Objective To measure the likelihood of delivery by caesarean section (C-section) for publicly insured births as compared with privately insured births, across all hospitals and within private hospitals. Design Repeated cross-sectional analysis. Setting The universe of hospital births in 15 regions of Chile. Participants 2 405 082 singleton births between 2001 and 2014. Outcome measures C-section rates by type of hospital and type of insurance; contribution to overall C-section rates of subgroups by type of insurance and type of hospital; adjusted OR of privately insured births delivered by C-section compared with publicly insured births, across all hospitals and within private hospitals; percentage of discharges related to maternal morbidity and mortality across groups; length of stay after delivery. Results An increasing percentage of publicly insured births occur in private facilities each year. Approximately three out of four publicly insured births in private hospitals are delivered by C-section. The adjusted odd of C-section delivery in a private maternity unit is lower for those privately insured than for those with public insurance: OR 0.6, 95% CI 0.56 to 0.64. There is no evidence that these women would have been more likely to have a C-section out of medical necessity. Conclusions We find an association between high C-section rates and publicly insured women delivering at private institutions in Chile, and show that this group is driving the overall high and growing rates. There is a need for a more informed surveillance on the part of the public insurance system of its private providers' C-section practices.