According to a recent study of 30-day acute-care hospital readmissions of Medicaid patients in 19 states:

• 9.4% of all Medicaid hospital admissions were readmissions
• The cost of Medicaid readmissions averaged $77 million per state
• Readmissions represented 12.5% of Medicaid payments for all hospitalizations
• 31.2% of readmissions fell under the diagnostic categories of mental and behavioral disorders, and diagnoses related to pregnancy, childbirth, and their complications

Source: "Medicaid Admissions And Readmissions: Understanding The Prevalence, Payment, And Most Common Diagnoses," Health Affairs, abstract only, August 2014, http://content.healthaffairs.org/content/33/8/1337.abstract