title: Incidence and timing of presentation of necrotizing enterocolitis in preterm infants.
abstract: OBJECTIVE
  To examine the variation in the incidence and to identify the timing of the presentation of necrotizing enterocolitis (NEC) in a cohort of preterm infants within the Canadian Neonatal Network (CNN).
  
  
  METHODS
  This was a population-based cohort of 16 669 infants with gestational age (GA) <33 weeks, admitted to 25 NICUs participating in the CNN between January 1, 2003, and December 31(,) 2008. Variations in NEC incidence among the participating NICUs for the study period were examined. We categorized early-onset NEC as occurring at <14 days of age and late-onset NEC occurring at ≥14 days. Multivariate logistic regression analysis was performed to identify risk factors for early-onset NEC.
  
  
  RESULTS
  The overall incidence of NEC was 5.1%, with significant variation in the risk adjusted incidence among the participating NICUs in the CNN. Early-onset NEC occurred at a mean of 7 days compared with 32 days for late-onset NEC. Early-onset NEC infants had lower incidence of respiratory distress syndrome, patent ductus treated with indomethacin, less use of postnatal steroids, and shorter duration of ventilation days. Multivariate logistic regression analysis identified that greater GA and vaginal delivery were associated with increased risk of early-onset NEC.
  
  
  CONCLUSIONS
  Among infants <33 weeks' gestation, NEC appears to present at mean age of 7 days in more mature infants, whereas onset of NEC is delayed to 32 days of age in smaller, lower GA infants. Further studies are required to understand the etiology of this disease process.
authors.affiliation: Department of Pediatrics, Alberta Children’s Hospital Research Institute for Child and Maternal Health, University of Calgary, Alberta, Canada. wendy.yee@albertahealthservices.ca
authors.forename: Wendy H
authors.initials: WH
authors.lastname: Yee
authors.forename: Amuchou Singh
authors.initials: AS
authors.lastname: Soraisham
authors.forename: Vibhuti S
authors.initials: VS
authors.lastname: Shah
authors.forename: Khalid
authors.initials: K
authors.lastname: Aziz
authors.forename: Woojin
authors.initials: W
authors.lastname: Yoon
authors.forename: Shoo K
authors.initials: SK
authors.lastname: Lee
mesh_terms: D002170:Canada; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D016208:Databases, Factual; D020345:Enterocolitis, Necrotizing / Q000175:diagnosis* / Q000453:epidemiology*; D005260:Female; D005865:Gestational Age; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D007235:Infant, Premature, Diseases / Q000175:diagnosis* / Q000453:epidemiology*; D007236:Infant, Small for Gestational Age; D019102:Infant, Very Low Birth Weight; D007363:Intensive Care Units, Neonatal; D008297:Male; D012307:Risk Factors