title: Respiratory distress syndrome and birth order in premature twins.
abstract: OBJECTIVE
  To determine the effect of birth order on respiratory distress syndrome (RDS) in the outcome of twins in a large premature population managed in a modern neonatal intensive care unit.
  
  
  METHODS
  An historical cohort study design was used to analyse the neonatal outcomes of 301 premature liveborn twin sibling pairs of between 23 and 31 weeks gestation from the Australia and New Zealand Neonatal Network 1995 database.
  
  
  RESULTS
  Among the 56 twin sibling pairs who were discordant for RDS, the second twin was affected in 41 cases (odds ratio (OR) 2.7, 95% confidence interval (CI) 1.5 to 5.3). The excess risk of RDS in the second twin increased with gestation and was statistically significant for twins above 29 weeks gestation (OR 4.4, 95% CI 1.6 to 15).
  
  
  CONCLUSIONS
  There is a significant increased risk of RDS associated with being the second born of premature twins, which appears to depend on gestation.
authors.affiliation: Department of Paediatrics, Mercy Hospital for Women, Clarendon Street, East Melbourne, Victoria 3002, Australia. doug.hacking@imm.ox.ac.uk
authors.forename: D
authors.initials: D
authors.lastname: Hacking
authors.forename: A
authors.initials: A
authors.lastname: Watkins
authors.forename: S
authors.initials: S
authors.lastname: Fraser
authors.forename: R
authors.initials: R
authors.lastname: Wolfe
authors.forename: T
authors.initials: T
authors.lastname: Nolan
mesh_terms: D001722:Birth Order; D001724:Birth Weight; D016001:Confidence Intervals; D036861:Delivery, Obstetric / Q000379:methods; D004200:Diseases in Twins; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D008297:Male; D016017:Odds Ratio; D011379:Prognosis; D012044:Regression Analysis; D012127:Respiratory Distress Syndrome, Newborn / Q000209:etiology*; D012189:Retrospective Studies; D012307:Risk Factors; D018709:Statistics, Nonparametric