Socioeconomic and health system determinants of maternal health inequities across Chinese provinces (2009–2021): a multivariate meta-regression analysis of regional heterogeneity in underlying mechanisms

Background: Despite China's significant reduction in maternal mortality rate (MMR), substantial inter-provincial disparities persist, reflecting uneven socioeconomic development and health system capacity. Previous studies have rarely examined the interplay of these factors using standardized inequality measures. This study quantifies maternal health inequalities across 31 Chinese provinces and identifies key socioeconomic and health system determinants. Methods: Using provincial panel data (2009-2021), we measured absolute and relative MMR disparities via the Slope Index of Inequality (SII) and Relative Index of Inequality (RII). Random-effects meta-regression models assessed how socioeconomic (population size, urbanization, college student numbers, total wealth, GDP per capita, insurance coverage) and health system variables (health workforce, beds, health expenditures per capita) influenced inequality, with stratification by eastern vs. central/western regions. Results: SII and RII varied considerably across provinces, indicating significant heterogeneity. Total wealth and higher education levels consistently reduced inequality, especially in central/western regions. In contrast, larger population size, urbanization, and uneven workforce distribution were associated with greater disparities. Health insurance had a protective effect mainly in less-developed areas. Paradoxically, higher health workforce density and rapid urbanization correlated with increased inequality, suggesting structural inefficiencies and unequal resource concentration. Conclusion: Household income, education, and insurance coverage are crucial for reducing maternal health disparities, whereas uneven urbanization and workforce allocation exacerbate them. Region-specific governance-focusing on fiscal transfers, education investment, and equitable health workforce distribution in central/western provinces, alongside efficiency improvements in the east-is essential for achieving Healthy China 2030 and SDG 3.1. Future policies must prioritize equity alongside average improvements.