title: Neonatal morbidity by week of gestational age for twins compared to singletons: a population-based cohort study.
abstract: OBJECTIVE
  Quantify neonatal morbidity by week of gestation for twins compared with singletons.
  
  
  METHODS
  We performed a population-based retrospective cohort study of all Ohio births from 2006 to 2007. Composite neonatal morbidity consisting of Apgar score < 7 at 5 minutes, assisted ventilation > 6 hours, neonatal transport, or seizures was compared between singletons and twins from 34 to 41 weeks.
  
  
  RESULTS
  Neonatal morbidity was the lowest in twins delivered at 37 completed weeks and 2 weeks later for singletons at 39 weeks. Twin morbidity rapidly increased after 37 weeks and reached 15.8% at 41 weeks versus the singleton morbidity rate of 3.4% at 41 weeks. Twins delivered at 39 weeks and beyond were more than twice as likely to incur neonatal morbidity compared with singletons.
  
  
  CONCLUSIONS
  The lowest rate of neonatal morbidity occurs at 37 weeks for twins versus 39 weeks for singleton births. The increased risk after 37 weeks for twins accelerates at a faster rate compared with that for singletons born past 39 weeks.
authors.affiliation: Division of Maternal-Fetal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio.
authors.forename: Katherine
authors.initials: K
authors.lastname: Wolfe
authors.affiliation: Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
authors.forename: Meredith
authors.initials: M
authors.lastname: Tabangin
authors.affiliation: Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
authors.forename: Jareen
authors.initials: J
authors.lastname: Meinzen-Derr
authors.affiliation: Division of Maternal-Fetal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio.
authors.forename: Candice
authors.initials: C
authors.lastname: Snyder
authors.affiliation: Division of Maternal-Fetal Medicine, University of South Alabama, Mobile, Alabama.
authors.forename: David
authors.initials: D
authors.lastname: Lewis
authors.affiliation: Division of Maternal-Fetal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio.
authors.forename: Emily
authors.initials: E
authors.lastname: DeFranco
mesh_terms: D001034:Apgar Score; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000453:epidemiology*; D008297:Male; D009017:Morbidity; D009820:Ohio / Q000453:epidemiology; D010360:Patient Transfer; D011247:Pregnancy; D011256:Pregnancy Outcome; D012121:Respiration, Artificial / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D012640:Seizures / Q000453:epidemiology; D014427:Twins