title: The search for objective criteria at the limit of viability.
abstract: BACKGROUND
  Defining the limit of viability among very preterm infants remains a difficult issue. A recent study suggested severity of intrauterine growth retardation as a decisive criterion, reporting very poor survival for infants born at </=28 weeks with birth weight <2nd centile.
  
  
  OBJECTIVE
  To check whether the above criterion can be confirmed in a similar analysis of German data.
  
  
  METHODS
  Analyses were based on German population-based data from Lower Saxony, including preterm neonates (22-28 weeks) without severe congenital malformations (n = 3,453), born 1991-1999. For the definition of growth retardation postnatal (<3rd, <10th centile) and antenatal (<3rd centile) reference values were used.
  
  
  RESULTS
  Depending on the definition used, proportions of growth retarded infants varied considerably (4-16%). Survival rates increased from 0 to 64%, arguing against considering infants <28 weeks' GA as a homogenous group with regard to their odds for survival.
  
  
  CONCLUSIONS
  There is an association between severity of growth retardation and VLBW mortality in general, but overinterpreting results from single studies may lead to dangerous conclusions. Data from preterm infants should be stratified by week of gestation.
authors.affiliation: Department of Epidemiology, Public Medicine and Healthcare Systems Research, Hannover Medical School, Hannover, Germany. bartels.dorothee@mh-hannover.de
authors.forename: Dorothee B
authors.initials: DB
authors.lastname: Bartels
authors.forename: Christian F
authors.initials: CF
authors.lastname: Poets
mesh_terms: D005317:Fetal Growth Retardation; D005328:Fetal Viability; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D007234:Infant, Premature; D007236:Infant, Small for Gestational Age; D012189:Retrospective Studies