Gestational age and 1-year hospital admission or mortality: a nation-wide population-based study

International audience ; Background: Describe the 1-year hospitalization and in-hospital mortality rates, in infants born after 31 weeks ofgestational age (GA).Methods: This nation-wide population-based study used the French medico-administrative database to assess thefollowing outcomes in singleton live-born infants (32–43 weeks) without congenital anomalies (year 2011): neonatalhospitalization (day of life 1 – 28), post-neonatal hospitalization (day of life 29 – 365), and 1-year in-hospital mortalityrates. Marginal models and negative binomial regressions were used.Results: The study included 696,698 live-born babies. The neonatal hospitalization rate was 9.8%. Up to 40 weeks,the lower the GA, the higher the hospitalization rate and the greater the likelihood of requiring the highest levelof neonatal care (both p < 0.001). The relative risk adjusted for sex and pregnancy-related diseases (aRR) reached21.1 (95% confidence interval [CI]: 19.2-23.3) at 32 weeks. The post-neonatal hospitalization rate was 12.1%. Theraw rates for post-neonatal hospitalization fell significantly from 32 – 40 and increased at 43 weeks and thispersisted after adjustment (aRR = 3.6 [95% CI: 3.3–3.9] at 32 and 1.5 [95% CI: 1.1–1.9] at 43 compared to 40 weeks).The main causes of post-neonatal hospitalization were bronchiolitis (17.2%), gastroenteritis (10.4%) ENT diseases(5.4%) and accidents (6.2%). The in-hospital mortality rate was 0.85‰, with a significant decrease (p < 0.001)according to GA at birth (aRR = 3.8 [95% CI: 2.4–5.8] at 32 and 6.6 [95% CI: 2.1–20.9] at 43, compared to 40 weeks.Conclusion: There’s a continuous change in outcome in hospitalized infants born above 31 weeks. Birth at 40 weeksgestation is associated with the lowest 1-year morbidity and mortality.