Medicaid prospective payment: case-mix increase.

South Carolina Medicaid implemented prospective payment by diagnosis-related group (DRG) for inpatient care. The rate of complications among newborns and deliveries doubled immediately. The case-mix index for newborns increased 66.6 percent, which increased the total Medicaid hospital expenditure 5.5 percent. Outlier payments increased total expenditure further. DRG distribution change among newborns has a large impact on spending because newborn complication DRGs have high weights. States adopting a DRG-based payment system for Medicaid should anticipate a greater increase in case mix than Medicare experienced.