title: The influence of mode of delivery on twin neonatal mortality in the US: variance by birth weight discordance.
abstract: OBJECTIVE
  The purpose of this study was to examine if neonatal mortality rates (NMR) based on birth weight discordance (BWD) differ based on mode of delivery.
  
  
  METHODS
  The population-based US "matched multiple birth" database (1995 to 1998) was used to examine the effect of vaginal/vaginal (VV) and cesarean/cesarean (CC) modes of delivery (MOD) on neonatal mortality (<28 days after birth). Births at <32 weeks, congenital malformations, chromosomal anomalies, and discordant MOD (vaginal/cesarean) were excluded. The association between MOD (with CC as the reference) and neonatal mortality was expressed as relative risks (RR) with 95% CI, derived from logistic regression models.
  
  
  RESULTS
  The NMR increased with increasing degrees of BWD regardless of mode of delivery. CC was associated with decreased NMR when BWD was between 20% and 40%, but this reached significance at BWD > or =40%; VV pairs had a 1.6-fold (95% CI 1.1-2.2) increased NMR compared with CC.
  
  
  CONCLUSIONS
  In twins with BWD <40%, MOD has no effect on NMR. Beyond or equal to 40% discordance, there was lower NMR with cesarean-cesarean delivery.
authors.affiliation: Division of Maternal-Fetal Medicine, Roberto Wood Johnson University Hospital/Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, New Brunswick, NJ, USA.
authors.forename: Eftichia V
authors.initials: EV
authors.lastname: Kontopoulos
authors.forename: Cande V
authors.initials: CV
authors.lastname: Ananth
authors.forename: John C
authors.initials: JC
authors.lastname: Smulian
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Vintzileos
mesh_terms: D000328:Adult; D001724:Birth Weight; D002585:Cesarean Section / Q000706:statistics & numerical data; D016208:Databases, Factual; D036861:Delivery, Obstetric / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D016015:Logistic Models; D011247:Pregnancy; D012307:Risk Factors; D014427:Twins; D014481:United States / Q000453:epidemiology