title: Neonatal death and morbidity in vertex-nonvertex second twins according to mode of delivery and birth weight.
abstract: OBJECTIVE
  The purpose of this study was to assess the risk of neonatal death and morbidity in vertex-nonvertex second twins according to the mode of delivery and birth weight.
  
  
  METHODS
  Data from a retrospective cohort study that was based on all twin births in the United States (1995-1997) were used.
  
  
  RESULTS
  A total of 15,185 vertex-nonvertex second twins were classified into 3 groups: (1) both twins were delivered by cesarean delivery (37.7%), (2) both twins were delivered vaginally (46.8%), and (3) the second twin was delivered by cesarean delivery after vaginal delivery of the first twin (15.5%). The risk of asphyxia-related neonatal deaths and morbidity was increased in the group in which both twins were delivered vaginally and the group in which both twins were delivered by cesarean delivery. The increase in neonatal death in the group in which both twins were delivered vaginally was stronger in the birth weight of < 1500 g. In contrast, in the group in which both twins were delivered vaginally and the group in which the second twin was delivered by cesarean delivery after the first twin was delivered vaginally, the increase in neonatal morbidity was greater in the group in which the birth weight was 1500 to 4000 g.
  
  
  CONCLUSIONS
  The risk of neonatal death and morbidity in second-born twins is higher in the group in which both twins were delivered vaginally and the group in which the second twin was delivered by cesarean delivery after the first twin was delivered vaginally compared with the group in which both twins were delivered by cesarean delivery.
authors.affiliation: OMNI Research Group, Division of Maternal-Fetal Medicine, Unveristy of Ottawa, Faculty of Medicine, Ottawa, Ontario, Canada. qyang@ohri.ca
authors.forename: Qiuying
authors.initials: Q
authors.lastname: Yang
authors.forename: Shi Wu
authors.initials: SW
authors.lastname: Wen
authors.forename: Yue
authors.initials: Y
authors.lastname: Chen
authors.forename: Daniel
authors.initials: D
authors.lastname: Krewski
authors.forename: Karen
authors.initials: K
authors.lastname: Fung Kee Fung
authors.forename: Mark
authors.initials: M
authors.lastname: Walker
mesh_terms: D000328:Adult; D001238:Asphyxia Neonatorum / Q000453:epidemiology* / Q000401:mortality; D001724:Birth Weight; D002585:Cesarean Section; D015331:Cohort Studies; D036861:Delivery, Obstetric / Q000379:methods*; D004200:Diseases in Twins / Q000453:epidemiology* / Q000401:mortality; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007746:Labor Presentation; D011247:Pregnancy; D012189:Retrospective Studies; D014427:Twins