Measuring severe neonatal morbidity using hospital discharge data in France

Background: Measuring infant health at birth is key for surveillance and research in obstetrics and neonatology, but there is no international consensus on morbidity indicators. The Neonatal Adverse Outcome Indicator (NAOI) is a composite indicator, developed in Australia, which measures the burden of severe neonatal morbidity using hospital discharge data. Objective: To evaluate the applicability of the NAOI in France for surveillance and research. Methods: We constituted a cohort of live births ≥24 weeks’ gestational age in Metropolitan France from 2014 to 2015 using hospital discharge, insurance claims and cause of death data. Outlier hospitals were identified using funnel plots of standardised morbidity ratios (SMR), and their coding patterns were assessed. We compared the NAOI and its component codes with published Australian and English data and estimated unadjusted and adjusted risk ratios for known risk factors for neonatal morbidity. Results: We included 1,459,123 births (511 hospitals). Twenty-eight hospitals had SMR above funnel plot control limits. Newborns with NAOI morbidities in these hospitals had lower mortality and shorter stays than in other hospitals. Amongst within-limit hospitals, NAOI prevalence was 4.8%, comparable to Australia (4.6%) and England (5.4%). Most individual components had a similar prevalence, with the exception of respiratory support, intravenous fluid procedures and infection. NAOI was lowest at 39 weeks (2.2%) with higher risks for maternal age ≥40 (relative risk [RR] 1.47, 95% confidence interval [CI] 1.42, 1.51), state medical insurance (RR 1.60, 95% CI 1.52, 1.68), male sex (RR 1.21, 95% CI 1.19, 1.23) and birthweight <3^rd percentile (RR 4.60, 95% CI 4.51, 4.69). Conclusions: The NAOI provides valuable information on population prevalence of severe neonatal morbidity and its risk factors. Whilst the prevalence was similar in high-income countries with comparable neonatal mortality levels, ensuring valid comparisons between countries and hospitals will require further work to harmonize coding procedures, especially for infection and respiratory morbidity.