title: Birth order and delivery interval: analysis of twin pair perinatal outcomes.
abstract: OBJECTIVE
  To determine whether second-born twins (B) have higher morbidity and mortality than first-born twins (A), using a paired analysis.
  
  
  METHODS
  We conducted a retrospective analysis of birth certificates and fetal and infant death certificates for 5138 twin pairs selected from those born in Washington State from 1989 to 2001. Twin A was vertex and delivered vaginally. Pairs were not size-discordant (< 20%) and had no malformations. Matched-pair odds ratios were calculated.
  
  
  RESULTS
  Twin B had more fetal distress (OR=6.0) and more low 5-min Apgar scores (OR=2.1) than Twin A, except at short delivery intervals. Pairs had relatively high rates of combined vaginal plus cesarean deliveries at delivery intervals 15 min.
  
  
  CONCLUSIONS
  If prompt vaginal delivery of Twin B does not occur, the benefits of vaginal delivery for Twin A might not outweigh the risks of distress and low Apgar scores in Twin B and vaginal plus cesarean delivery for the mother.
authors: Biology Department, Seattle University, Seattle, Washington 98122, USA. rhartley@seattleu.edu
authors: Rebecca S
authors: RS
authors: Hartley
authors: Jane
authors: J
authors: Hitti
mesh_terms: D001034:Apgar Score; D001722:Birth Order; D001946:Breech Presentation; D002585:Cesarean Section; D036861:Delivery, Obstetric; D005260:Female; D005313:Fetal Death / Q000453:epidemiology; D005316:Fetal Distress / Q000453:epidemiology; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D007746:Labor Presentation; D008297:Male; D016017:Odds Ratio; D011247:Pregnancy; D011256:Pregnancy Outcome; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D014427:Twins