Are birth outcomes in non high-risk children related to hospital birth volumes? A systematic review

BACKGROUND: There is convincing evidence that birth in hospitals with high birth volumes increases the chance of healthy survival in high-risk infants. However, it is unclear whether this is true also for non high-risk infants. OBJECTIVES: Systematic review on effects of hospital’s birth volume on mortality, mode of delivery, readmissions, complications and developmental delays in non high-risk infants. SEARCH STRATEGY: EMBASE and Medline supplemented by citing and cited literature of included studies and expert panel highlighting additional literature, published between Janu-ary/2000 and February/2020. SELECTION CRITERIA: Publications in English or German language reporting effects of birth volumes on mortality in term or all births in countries with neonatal mortality <5/1000. DATA COLLECTION AND ANALYSIS: We undertook a double-independent title-abstract- and full-text screening and extraction of study characteristics, critical appraisal and outcomes in a qualitative evidence synthesis. MAIN RESULTS: 13 retrospective studies with mostly acceptable quality totaling 6.254.431 births and 51.907.405 deliveries were included. Heterogeneous volume-thresholds, risk ad-justments, outcomes and populations hindered a meta-analysis. Qualitatively, four of six studies reported significantly higher perinatal mortality in lower birth volume hospitals. Volume-outcome effects on neonatal mortality (n=7), stillbirths (n=3), maternal mortality (n=1), caesar-ean sections (n=2), maternal (n=1) and neonatal complications (n=1) were inconclusive. CONCLUSION: Analyzed studies indicate higher rates of perinatal mortality in hospitals with low birth volumes. Due to heterogeneity of studies, data synthesis was complicated and a meta-analysis was not possible. Therefore international core outcome sets should be defined and implemented in perinatal registries.