title: Population based trends in mortality, morbidity and treatment for very preterm- and very low birth weight infants over 12 years.
abstract: BACKGROUND
  Over the last two decades, improvements in medical care have been associated with a significant increase and better outcome of very preterm (VP, < 32 completed gestational weeks) and very low birth weight (VLBW, < 1500 g) infants. Only a few publications analyse changes of their short-term outcome in a geographically defined area over more than 10 years. We therefore aimed to investigate the net change of VP- and VLBW infants leaving the hospital without major complications.
  
  
  METHODS
  Our population-based observational cohort study used the Minimal Neonatal Data Set, a database maintained by the Swiss Society of Neonatology including information of all VP- and VLBW infants. Perinatal characteristics, mortality and morbidity rates and the survival free of major complications were analysed and their temporal trends evaluated.
  
  
  RESULTS
  In 1996, 2000, 2004, and 2008, a total number of 3090 infants were enrolled in the Network Database. At the same time the rate of VP- and VLBW neonates increased significantly from 0.87% in 1996 to 1.10% in 2008 (p < 0.001). The overall mortality remained stable by 13%, but the survival free of major complications increased from 66.9% to 71.7% (p < 0.01). The percentage of infants getting a full course of antenatal corticosteroids increased from 67.7% in 1996 to 91.4% in 2008 (p < 0.001). Surfactant was given more frequently (24.8% in 1996 compared to 40.1% in 2008, p < 0.001) and the frequency of mechanical ventilation remained stable by about 43%. However, the use of CPAP therapy increased considerably from 43% to 73.2% (p < 0.001). Some of the typical neonatal pathologies like bronchopulmonary dysplasia, necrotising enterocolitis and intraventricular haemorrhage decreased significantly (p ≤ 0.02) whereas others like patent ductus arteriosus and respiratory distress syndrome increased (p < 0.001).
  
  
  CONCLUSIONS
  Over the 12-year observation period, the number of VP- and VLBW infants increased significantly. An unchanged overall mortality rate and an increase of survivors free of major complication resulted in a considerable net gain in infants with potentially good outcome.
authors.affiliation: Division of Neonatology, University Hospital Zurich, Zurich, Switzerland. ch.rueegger@gmail.com
authors.forename: Christoph
authors.initials: C
authors.lastname: Rüegger
authors.forename: Markus
authors.initials: M
authors.lastname: Hegglin
authors.forename: Mark
authors.initials: M
authors.lastname: Adams
authors.forename: Hans Ulrich
authors.initials: HU
authors.lastname: Bucher
mesh_terms: D015331:Cohort Studies; D005260:Female; D006801:Humans; D007226:Infant Mortality / Q000639:trends*; D007231:Infant, Newborn; D007234:Infant, Premature; D007235:Infant, Premature, Diseases / Q000453:epidemiology*; D019102:Infant, Very Low Birth Weight; D015931:Intensive Care, Neonatal / Q000706:statistics & numerical data / Q000639:trends*; D053208:Kaplan-Meier Estimate; D007902:Length of Stay / Q000706:statistics & numerical data / Q000639:trends; D008297:Male; D012042:Registries; D013557:Switzerland / Q000453:epidemiology