ArticlePediatric research2026
Spatial analysis of cross-boundary hospitalizations of very low birth weight infants in Japan.
Article in Pediatric research, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
What it found
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Authors and funding
3 authors.
Funding
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Abstract
backgroundVery low birth weight (VLBW) infants require prompt access to intensive care for survival and optimal outcomes. While Japan manages healthcare through 335 Secondary Medical Areas (SMAs) across 47 prefectures, cross-boundary patient flow remains poorly characterized. We evaluated spatial patterns of admission of VLBW infants within Japan's perinatal system, hypothesizing that cross-boundary hospitalizations follow distinct patterns reflecting structural reliance on external resources.
methodsWe conducted a retrospective, population-based study using nationwide administrative claims data for VLBW infants born between 2021 and 2023. Spatial indicators, including the localization index and outflow balance, were analyzed alongside travel distances to characterize cross-boundary patient flow and travel burden.
resultsAmong 12,093 infants, 56% were admitted within their SMA and 92% within their prefecture. Spatial analysis identified distinct regional patterns: SMAs with Comprehensive Perinatal Medical Centers showed high localization indices and inflow, whereas outflow hotspots surrounding Tokyo were identified in populous SMAs without any such centers. Furthermore, northern prefectures exhibited clusters of longer cross-SMA travel distances.
conclusionGeographical variation in hospitalization revealed structural reliance on external resources and regional inequities in access. Integrating spatial context into perinatal planning provides a fundamental basis for ensuring adequate capacity, thereby fostering a resilient, equitable neonatal care system. IMPACT: Nationwide spatial analysis revealed distinct patterns of cross-boundary hospitalization among very low birth weight infants in Japan, reflecting a structural reliance on external regional resources. This study provides the first population-based visualization of regionalized care reliance, shifting the analytical focus from individual facility performance to system-wide patient flow indicators. The identification of specific regional vulnerabilities-metropolitan resource gaps and northern travel burdens-demonstrates the critical need to integrate spatial context into perinatal healthcare planning.
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Registered trials
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