CHS-DRG 2.0 and insurance-specific patient cost sharing in gestational diabetes admissions: a regression discontinuity in time study.

Objectives: Diagnosis-related group reform aims to restrain inpatient spending, but obstetric evaluations commonly emphasize average hospital costs rather than insurance-specific patient cost sharing. We evaluated early discontinuities associated with CHS-DRG 2.0 in hospitalization costs, out-of-pocket (OOP) payment, self-pay ratio, and selected perinatal outcomes among gestational diabetes mellitus (GDM) admissions. Methods: We analyzed 8,690 singleton GDM delivery admissions at a tertiary maternal and child health hospital in Fujian, China. The main cohort excluded eight stays exceeding 60 days, consistent with the policy DRG-management scope. We classified policy period from the recorded admission date under the provincial rule: admissions before 1 January 2025, including cross-cutoff stays, remained under the prior payment arrangement; admissions on or after that date entered the CHS-DRG 2.0 policy period. Actual DRG assignment and claim settlement were unavailable. Local linear regression discontinuity in time models used triangular kernels, data-driven bandwidths, robust bias-corrected confidence intervals, and discharge-day-clustered standard errors. Results: The admission-date cutoff was not associated with a precise discontinuity in total hospitalization cost (estimate, -42.10 CNY; 95% CI, -1,158.46 to 1,074.26; Conclusion: The admission-date policy boundary was associated with a larger reduction in relative patient cost sharing among resident-insured GDM admissions. Discontinuous admission density at the cutoff and possible concurrent calendar-time changes limit causal attribution and preclude inference about a specific payment mechanism. Payment-reform evaluations should jointly assess insurance-specific patient cost sharing, provider expenditure, and clinical outcomes.