title: The Likelihood of Change in Fetal Presentation During the Third Trimester in Twin Pregnancies.
abstract: OBJECTIVE
  To estimate the likelihood and identify predictors of spontaneous fetal version during the third trimester in twins using data from a multicenter randomized controlled trial on mode of delivery in twin pregnancies.
  
  
  METHODS
  Women with twin pregnancies after 32 weeks of gestation in which twin A was vertex were randomized to planned cesarean or planned vaginal delivery. In the current study we analyzed the likelihood of a spontaneous version of any of the twins between ultrasound assessment at the time of randomization and delivery.
  
  
  RESULTS
  A total of 2,603 women were analyzed. Twin A tended to persist in the vertex presentation after 32 weeks of gestation with a spontaneous version rate to nonvertex presentation of 3.0% (95% confidence interval [CI] 2.3-3.7%). Twin B was less stable and underwent spontaneous version in 24.8% (95% CI 23.1-26.5%) of cases; the rate remained higher than 20% even after 34 weeks of gestation. On multivariable analysis, twin A was more likely to undergo version when twin B was smaller (adjusted odds ratio [OR] 2.0, 95% CI 1.04-3.3), when twin B was breech (adjusted OR 3.7, 95% CI 2.2-6.4) or transverse (adjusted OR 2.9, 95% CI 1.6-5.5), and when the interval to delivery exceeded 4 weeks (adjusted OR 2.5, 95% CI 1.3-5.0). Twin B was more likely to undergo version when it was in the breech presentation (adjusted OR 1.7, 95% CI 1.4-2.1) or transverse lie (adjusted OR 3.1, 95% CI 2.5-3.9) compared with vertex presentation, when it was smaller (adjusted OR 1.7, 95% CI 1.1-2.0), when the interval to delivery exceeded 4 weeks (adjusted OR 1.7, 95% CI 1.3-2.4), and in multiparous women (adjusted OR 1.3, 95% CI 1.04-1.5).
  
  
  CONCLUSIONS
  The likelihood of spontaneous version of twin A after 32 weeks of gestation is low when twin A is in the vertex presentation but is much higher for twin B, even late during the third trimester.
  
  
  BACKGROUND
  ClinicalTrials.gov, www.clinicaltrials.gov, NCT00187369.
  
  
  METHODS
  II.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology and the Department of Newborn & Developmental Paediatrics, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Nir
authors.initials: N
authors.lastname: Melamed
authors.forename: Jellena
authors.initials: J
authors.lastname: Wong
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Asztalos
authors.forename: Hadar
authors.initials: H
authors.lastname: Rosen
authors.forename: Rania
authors.initials: R
authors.lastname: Okby
authors.forename: Jon
authors.initials: J
authors.lastname: Barrett
mesh_terms: D000328:Adult; D001946:Breech Presentation; D002585:Cesarean Section; D005260:Female; D006801:Humans; D007746:Labor Presentation; D016015:Logistic Models; D016017:Odds Ratio; D011247:Pregnancy; D011263:Pregnancy Trimester, Third / Q000502:physiology*; D059285:Pregnancy, Twin / Q000502:physiology*; D016216:Ultrasonography, Prenatal