Equity_Adjusted Safe_Delivery Thresholds: A Global Causal Analysis of Institutional Birth Coverage and Maternal Mortality in 182 Countries, 2000 to 2022

AbstractsO_ST_ABSBackgroundC_ST_ABSMaternal mortality remains far above the Sustainable Development Goal (SDG) target in many settings, and global strategies lack an empirically derived coverage threshold for "safe" delivery. MethodsWe assembled a longitudinal panel of 2 184 country-year observations from 182 countries (2000-22), linking UN Maternal Mortality Estimation Inter-agency Group estimates with WHO and World Bank indicators. The primary exposure was institutional-birth coverage (% of livebirths in health facilities); the outcome was maternal mortality ratio (MMR; deaths per 100 000 livebirths). Using two-way fixed-effects models with restricted cubic splines, adjusted for anaemia prevalence and adolescent birth rate, we estimated the within-country association between institutional births and log(MMR). We then applied Hansen-type panel threshold regression to identify coverage levels at which the slope of this association changed, and repeated analyses by WHO region. FindingsMedian institutional-birth coverage was 72{middle dot}4% (IQR 54{middle dot}2-90{middle dot}7) and median MMR 173 deaths per 100 000 livebirths (81-328). Globally, each 10-percentage-point increase in institutional births was associated with a 7{middle dot}8% (95% CI 6{middle dot}1-9{middle dot}5) reduction in log(MMR). Threshold analysis identified a single global inflection at 70{middle dot}2% coverage (95% CI [~]68-72). Below this threshold, each 10-point increase in institutional births was associated with a 12{middle dot}6% (10{middle dot}2-14{middle dot}8) reduction in log(MMR), compared with 4{middle dot}1% (2{middle dot}5-5{middle dot}7) above the threshold--an almost three-fold difference in marginal effect. Region-specific thresholds ranged from 65% in the African Region to over 90% in the Western Pacific. InterpretationSeventy per cent institutional-birth coverage represents a "safe-delivery" threshold: below this level, expanding facility births yields large reductions in maternal mortality; above it, further gains require investments in quality of care, emergency obstetric capacity, and equity. Embedding this empirically derived threshold into SDG 3{middle dot}1 and universal health coverage monitoring could sharpen accountability, guide resource allocation, and accelerate progress towards ending preventable maternal deaths. FundingNone.