title: Optimal timing for term delivery of twin pregnancies: a population-based study.
abstract: OBJECTIVE
  The objective of this study was to examine the risk of adverse neonatal outcomes after twin delivery according to gestational age.
  
  
  METHODS
  The U.S. Natality Database from 2007 to 2010 was reviewed. Inclusion criteria were twin deliveries and gestational age of 37 to 42 weeks. Exclusion criteria were congenital anomalies and missing/incomplete data. Cases were subdivided by gestational age into early term, term, and late term. Singleton pregnancies matched by delivery time and location were selected as controls. Outcome variables included were low Apgar score, assisted ventilation, neonatal intensive care unit admission, surfactant/antibiotic use, seizures, and birth injury. Logistic regression analysis was used to calculate adjusted odds ratios according to gestational age and plurality, using singleton term as reference.
  
  
  RESULTS
  A total of 220,169 twin and 270,540 singleton deliveries were identified. The risk of adverse neonatal outcomes for twins was higher than for singletons. For twins, the distribution of the risks of the composite of adverse neonatal outcomes was linear, being the lowest at early term and the highest at late term, whereas the distribution for singletons was u-shaped being lowest at term compared with early and late term.
  
  
  CONCLUSIONS
  Twins are at higher risk of suboptimal neonatal outcomes than singletons, but do better when delivered at early term rather than term or late term.
authors.affiliation: Department of Obstetrics and Gynecology, Wayne State University/Detroit Medical Center, Detroit, Michigan.
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: Vilchez
authors.affiliation: C.S. Mott Center for Human Growth and Development, Wayne State University, Detroit, Michigan.
authors.forename: Jing
authors.initials: J
authors.lastname: Dai
authors.affiliation: Department of Obstetrics and Gynecology, Wayne State University/Detroit Medical Center, Detroit, Michigan.
authors.forename: Luis R
authors.initials: LR
authors.lastname: Hoyos
authors.affiliation: Department of Obstetrics and Gynecology, Wayne State University/Detroit Medical Center, Detroit, Michigan.
authors.forename: Anushka
authors.initials: A
authors.lastname: Chelliah
authors.affiliation: Department of Obstetrics and Gynecology, Wayne State University, Detroit, Michigan.
authors.forename: Ray
authors.initials: R
authors.lastname: Bahado-Singh
authors.affiliation: C.S. Mott Center for Human Growth and Development, Wayne State University, Detroit, Michigan.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Sokol
mesh_terms: D001034:Apgar Score; D036861:Delivery, Obstetric / Q000706:statistics & numerical data*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007223:Infant; D007226:Infant Mortality; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D016015:Logistic Models; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis*; D011256:Pregnancy Outcome; D059285:Pregnancy, Twin / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D047929:Term Birth; D013997:Time Factors; D014481:United States