Association between primary health care system strengthening and maternal-neonatal health outcomes in low‑income and lower‑middle‑income countries: a cross‑sectional ecological study

Low‑income countries (LICs) and lower‑middle‑income countries (LMICs) bear a disproportionate burden of maternal and neonatal mortality. Primary health care (PHC) is viewed as foundational for equitable outcomes, but evidence linking specific PHC system components to mortality reductions in these settings remains limited. This cross‑sectional ecological study analysed data from 47 countries (18 LICs, 29 LMICs) using the PHCPI Trailblazer Vital Signs Profile, supplemented with WHO Global Health Expenditure Database, World Bank Development Indicators, and WHO MNCAH data. Independent variables included PHC financing (expenditure per capita, government share), capacity (physician and nurse/midwifery density), performance (service coverage, quality, access scores), and equity (equity U5MR, equity RMNCH). Dependent variables were maternal mortality ratio (MMR) and neonatal mortality rate (NMR) for 2020. Analyses included descriptive statistics, Pearson correlations, multiple linear regression, comparative analysis by income group, K‑means cluster analysis, and exploratory path analysis (decomposition of statistical associations, not causal mediation). Median MMR was 398/100 000 (IQR 267–523) in LICs versus 259/100 000 (IQR 154–464) in LMICs. PHC expenditure per capita correlated negatively with MMR ( r = -0.52, p < 0.001); service coverage score correlated negatively with NMR ( r = -0.48, p = 0.001). After adjustment, each $10 increase in PHC expenditure per capita was associated with a 12.4% reduction in MMR (β = -0.124, 95% CI -0.198 to -0.050, p = 0.002). Service coverage score was the strongest predictor of NMR (β = -0.067, 95% CI -0.104 to -0.030, p = 0.001). Exploratory path analysis indicated that a statistically shared portion (34.2%) of the equity‑mortality association was attributable to service coverage, but causal mediation cannot be inferred from cross‑sectional data. Cluster analysis identified four PHC system archetypes: “Comprehensive Performers” ( n = 8), “Equity‑Focused Achievers” ( n = 12), “Resource‑Constrained Strugglers” ( n = 19), and “Financing‑Limited Systems” ( n = 8) (F = 14.32, p < 0.001). Strengthening PHC systems through increased financing, prioritization of skilled birth attendance, and equity‑focused interventions is associated with substantial reductions in maternal and neonatal mortality in LICs and LMICs. The findings support the inverse equity hypothesis and suggest targeted investments in PHC capacity and performance could accelerate progress toward SDG targets for maternal and child health.