Wealth-related inequality across the maternal and child continuum of care in low- and middle-income countries: a cross-country panel analysis using the slope index of inequality

Reducing wealth-related inequalities in maternal and child health remains central to universal health coverage (UHC). Prior cross-country analyses have mainly described inequality at single stages of care or relied on simple rich-poor comparisons. Less is known about how country-level structural factors are associated with inequality at different points along the continuum of care. This study constructed a country-year panel covering 124 low- and middle-income countries (LMICs) from 2000 to 2023, drawing on the WHO Health Inequality Data Repository, the UNICEF/WHO/World Bank Joint Malnutrition Estimates, the UN Inter-agency Group for Child Mortality Estimation, and World Bank World Development Indicators. Wealth-related inequality at each of 11 continuum stages was measured using the slope index of inequality (SII), computed from all five wealth quintiles and harmonized so that positive values indicate disadvantage among the poorest. Country-level structural correlates were examined using ordinary least squares models with country and year fixed effects and country-clustered standard errors. Additional sensitivity analyses applied within-stage z-standardization to SII, used a balanced four-stage core, reclassified ANC 1 + as facility-dependent, and substituted domestic general government health expenditure for total current health expenditure. Wealth-related inequality followed a non-monotonic pattern across the continuum. Inequality was modest at initial antenatal contact (mean SII = 4.4 percentage points), rose sharply through sustained antenatal care (34.5), skilled birth attendance (46.6), and facility delivery (45.6), declined at the infant-feeding stage with reversed gradients for early and exclusive breastfeeding (-3.0 and -6.6), and rose again for child nutrition and survival outcomes. In country- and year-fixed-effects models, female secondary school enrollment and current health expenditure as a share of GDP were associated with lower mean and peak inequality. After within-stage z-standardization, female secondary school enrollment remained negatively associated with mean-z (β = -0.009, p < 0.001) and peak-z (β = -0.009, p = 0.003), whereas current health expenditure was not statistically significant. Facility-stage interactions remained significant when ANC 1 + was reclassified as facility-dependent, and domestic general government health expenditure was negative in a separate sensitivity model. Wealth-related inequality in maternal and child health is highly stage-specific. Female secondary education is consistently associated with narrower absolute wealth gaps, including after stage-level standardization. The association between health expenditure and absolute inequality was sensitive to outcome specification and should therefore be interpreted cautiously.