Hospital Mergers, Hospital Choice, and Care Quality for Pregnant Enrollees in Medicaid.

Importance: Despite increasing consolidation in the US hospital market, little is known about how these mergers influence labor and delivery admissions and obstetric outcomes for patients with Medicaid. Objective: To assess whether hospital mergers are associated with changes in patient flows to hospitals and care quality for pregnant Medicaid enrollees. Design, Setting, and Participants: This cross-sectional study used a stacked difference-in-differences design to examine mergers occurring between 2004 and 2011. Changes in outcomes were examined in the 3 years before vs 3 years after a merger. Estimates were compared by urban vs rural settings and for Medicaid patients relative to privately insured patients. Labor and delivery admissions in 9 US states accounted for approximately 25% of all Medicaid-covered births nationwide during the study period. Medicaid-enrolled patients admitted for labor and delivery residing in counties that experienced a single hospital merger (intervention) or matched comparison counties without a merger during the same period were included. The analysis took place between December 2023 and April 2025. Exposure: Residing in a county that experienced a hospital merger. Outcomes: Outcomes included patient travel distance for delivery, admissions to safety net hospitals, and admissions to hospitals with a neonatal intensive care unit (NICU), indicating advanced obstetric capabilities. Obstetric quality outcomes included obstetric trauma for instrument-assisted and non-instrument-assisted admissions and in-hospital mortality. Results: The analysis included 527 499 Medicaid labor and delivery admissions across 30 merger and 28 nonmerger counties. The mean (SD) age across Medicaid labor and delivery admissions was 25.8 (5.9) years, and all were female individuals. In addition, 15.4% were Black, 19.9% were Hispanic, and 20.5% were White individuals. County-level exposure to a merger was associated with an adjusted 0.5-mile (95% CI, 0.1-1.0) increase in travel distance (an 8% increase from the 6.3-mile premerger baseline), a 9.2-percentage point (95% CI, 2.3-16.1) increase in admissions to safety net hospitals, and a 7.9-percentage point (95% CI, -11.2 to -4.6) decrease in admissions to NICU-equipped hospitals. One obstetric trauma measure (among non-instrument-assisted deliveries) increased slightly (0.4 percentage points; 95% CI, 0.2-0.6), whereas in-hospital mortality was unchanged. Urban counties experienced a decrease in admissions to NICU-equipped hospitals, whereas rural counties experienced increases. Compared with privately insured patients, Medicaid enrollees had larger increases in travel distance (0.6; 95% CI, 0.0-1.1) and safety net admissions (6.8; 95% CI, 1-12.6), but similar changes in NICU-equipped hospital admissions (-0.1; 95% CI, -2.4 to 2.3). Conclusions and Relevance: This cross-sectional study of labor and delivery admissions among patients with Medicaid found that hospital mergers were associated with an increased probability of admission to safety-net hospitals, lower probability of NICU-equipped hospitals, and worsening in 1 obstetric quality metric. These changes differed for Medicaid vs commercially insured patients and varied among Medicaid patients in urban vs rural markets. The findings underscore the importance of considering local market structure and potential adverse impacts on low-income populations when evaluating proposed hospital mergers.