title: Risk of uterine rupture among women attempting vaginal birth after cesarean with an unknown uterine scar.
abstract: OBJECTIVE
  The purpose of this study was to estimate the association of uterine rupture and previous incision type, either unknown or low transverse, among women who attempt a trial of labor after 1 previous cesarean delivery.
  
  
  METHODS
  We conducted a secondary analysis of a prospective multicenter observational study of 15,519 women with term singletons who attempted a trial of labor after 1 previous cesarean delivery. Odds ratios for the association between uterine incision location, either unknown or low transverse, and uterine rupture were estimated with the use of multivariable logistic regression.
  
  
  RESULTS
  Between 1999 and 2002, 99 of the 15,519 women (0.64%) who attempted a trial of labor after 1 previous cesarean delivery experienced a uterine rupture. Pregnant women with an unknown scar had lower odds of uterine rupture (adjusted odds ratio, 0.71; 95% confidence interval, 0.37-1.37) compared with women with a known low transverse scar. Other adverse maternal outcomes did not differ between the 2 groups of women.
  
  
  CONCLUSIONS
  Among this cohort, women with an unknown uterine incision who attempted a trial of labor were not at increased risk of uterine rupture compared with women with a known low transverse incision.
authors: Department of Obstetrics and Gynecology, School of Medicine, University of North Carolina, Chapel Hill, School of Medicine, Chapel Hill, NC.
authors: Dana
authors: D
authors: Smith
authors: Department of Obstetrics and Gynecology, School of Medicine, University of North Carolina, Chapel Hill, School of Medicine, Chapel Hill, NC.
authors: Elizabeth
authors: E
authors: Stringer
authors: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, School of Medicine, Chapel Hill, NC.
authors: Catherine J
authors: CJ
authors: Vladutiu
authors: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical School, Dallas, TX.
authors: Ashley Hickman
authors: AH
authors: Zink
authors: Department of Obstetrics and Gynecology, School of Medicine, University of North Carolina, Chapel Hill, School of Medicine, Chapel Hill, NC. Electronic address: Robert_Strauss@med.unc.edu.
authors: Robert
authors: R
authors: Strauss
mesh_terms: D000293:Adolescent; D000328:Adult; D002585:Cesarean Section; D002921:Cicatrix; D005260:Female; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome; D011446:Prospective Studies; D014597:Uterine Rupture / Q000453:epidemiology* / Q000209:etiology; D014599:Uterus / Q000473:pathology*; D016064:Vaginal Birth after Cesarean / Q000009:adverse effects*; D055815:Young Adult
keywords: trial of labor; unknown scar; uterine rupture; vaginal birth after cesarean delivery