Neonatal Intensive Care Capacity and Neonatal Mortality Across OECD Countries: A Longitudinal Two-Way Fixed-Effects Analysis, 2015–2023

Background and Aims: Neonatal intensive care unit (NICU) capacity is a key component of neonatal health systems, but a greater bed supply may not necessarily improve population-level neonatal outcomes. We examined whether national NICU bed capacity was associated with neonatal mortality across OECD countries and whether this relationship exhibited a nonlinear threshold or plateau.
Methods: We conducted a longitudinal ecological panel study using data from the OECD, United Nations, and World Bank for 2015–2023. NICU capacity was defined as the number of neonatal ICU beds per 1,000 live births, and neonatal mortality per 1,000 live births was the primary outcome. The analytic sample included 149 country-year observations from 24 OECD countries. Two-way fixed-effects regression models incorporated country and year fixed effects, with country-clustered robust standard errors. The models were adjusted for low-birthweight prevalence, GDP per capita, and health expenditure per capita. Nonlinearity was assessed using restricted cubic splines. Multiple sensitivity analyses were performed.
Results: The median NICU capacity was 3.77 beds per 1,000 live births (IQR, 2.48–5.71), and the median neonatal mortality rate was 2.2 per 1,000 live births (IQR, 1.8–2.7). In the fully adjusted model, NICU capacity was not associated with neonatal mortality (β=−0.072; 95% CI, −0.276 to 0.133; p=0.476). Spline analyses revealed no evidence of an overall association or nonlinearity. Sensitivity analyses yielded consistent findings.
Conclusion: Greater national NICU bed capacity was not consistently associated with lower neonatal mortality, and no robust threshold or plateau was identified. Therefore, capacity planning should consider staffing, regionalization, accessibility, case volume, and organization of care in addition to bed numbers.