title: Lower uterine segment thickness to prevent uterine rupture and adverse perinatal outcomes: a multicenter prospective study.
abstract: BACKGROUND
  Choice of delivery route after previous cesarean delivery can be difficult because both trial of labor after cesarean delivery and elective repeat cesarean delivery are associated with risks. The major risk that is associated with trial of labor after cesarean delivery is uterine rupture that requires emergency laparotomy.
  
  
  OBJECTIVE
  This study aimed to estimate the occurrence of uterine rupture during trial of labor after cesarean delivery when lower uterine segment thickness measurement is included in the decision-making process about the route of delivery.
  
  
  METHODS
  In 4 tertiary-care centers, we prospectively recruited women between 34 and 38 weeks of gestation who were contemplating a vaginal birth after a previous single low-transverse cesarean delivery. Lower uterine segment thickness was measured by ultrasound imaging and integrated in the decision of delivery route. According to lower uterine segment thickness, women were classified in 3 risk categories for uterine rupture: high risk (<2.0 mm), intermediate risk (2.0-2.4 mm), and low risk (≥2.5 mm). Our primary outcome was symptomatic uterine rupture, which was defined as requiring urgent laparotomy. We calculated that 942 women who were undergoing a trial of labor after cesarean delivery should be included to be able to show a risk of uterine rupture <0.8%.
  
  
  RESULTS
  We recruited 1856 women, of whom 1849 (99%) had a complete follow-up data. Lower uterine segment thickness was <2.0 mm in 194 women (11%), 2.0-2.4 mm in 217 women (12%), and ≥2.5 mm in 1438 women (78%). Rate of trial of labor was 9%, 42%, and 61% in the 3 categories, respectively (P<.0001). Of 984 trials of labor, there were no symptomatic uterine ruptures, which is a rate that was lower than the 0.8% expected rate (P=.0001).
  
  
  CONCLUSIONS
  The inclusion of lower uterine segment thickness measurement in the decision of the route of delivery allows a low risk of uterine rupture during trial of labor after cesarean delivery.
authors.affiliation: Department of Obstetrics & Gynaecology, Faculty of Medicine, Hôpitaux Universitaires de Genève, Université de Genève, Switzerland.
authors.forename: Nicole
authors.initials: N
authors.lastname: Jastrow
authors.affiliation: Department of Obstetrics & Gynaecology, Faculty of Medicine, Centre de recherche du Centre hospitalier universitaire de Québec, Université Laval, Québec, QC, Canada.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Demers
authors.affiliation: Department of Obstetrics & Gynaecology, Faculty of Medicine, Hôpital Sainte-Justine, Université de Montréal, Montréal, QC, Canada.
authors.forename: Nils
authors.initials: N
authors.lastname: Chaillet
authors.affiliation: Department of Obstetrics & Gynaecology, Faculty of Medicine, Centre de recherche du Centre hospitalier universitaire de Québec, Université Laval, Québec, QC, Canada.
authors.forename: Mario
authors.initials: M
authors.lastname: Girard
authors.affiliation: Department of Obstetrics & Gynaecology, Faculty of Medicine, Hôpital Sainte-Justine, Université de Montréal, Montréal, QC, Canada.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gauthier
authors.affiliation: Department of Obstetrics & Gynaecology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC, Canada.
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Pasquier
authors.affiliation: Department of Social and Preventive Medicine, Faculty of Medicine, Université Laval, Québec, QC, Canada.
authors.forename: Belkacem
authors.initials: B
authors.lastname: Abdous
authors.affiliation: Department of Obstetrics & Gynaecology, Faculty of Medicine, Centre de recherche du Centre hospitalier universitaire de Québec, Université Laval, Québec, QC, Canada.
authors.forename: Chantale
authors.initials: C
authors.lastname: Vachon-Marceau
authors.affiliation: Department of Social and Preventive Medicine, Faculty of Medicine, Université Laval, Québec, QC, Canada.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Marcoux
authors.affiliation: Department of Obstetrics & Gynaecology, Faculty of Medicine, Hôpitaux Universitaires de Genève, Université de Genève, Switzerland.
authors.forename: Olivier
authors.initials: O
authors.lastname: Irion
authors.affiliation: Department of Obstetrics & Gynaecology, Faculty of Medicine, Centre de recherche du Centre hospitalier universitaire de Québec, Université Laval, Québec, QC, Canada.
authors.forename: Normand
authors.initials: N
authors.lastname: Brassard
authors.affiliation: Department of Obstetrics & Gynaecology, Faculty of Medicine, Hôpitaux Universitaires de Genève, Université de Genève, Switzerland.
authors.forename: Michel
authors.initials: M
authors.lastname: Boulvain
authors.affiliation: Department of Obstetrics & Gynaecology, Faculty of Medicine, Centre de recherche du Centre hospitalier universitaire de Québec, Université Laval, Québec, QC, Canada; Department of Social and Preventive Medicine, Faculty of Medicine, Université Laval, Québec, QC, Canada. Electronic address: emmanuel.bujold@crchudequebec.ulaval.ca.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Bujold
mesh_terms: D000328:Adult; D000066491:Clinical Decision-Making; D036861:Delivery, Obstetric / Q000379:methods*; D005260:Female; D006801:Humans; D009929:Organ Size; D011247:Pregnancy; D011446:Prospective Studies; D018570:Risk Assessment; D014219:Trial of Labor; D016216:Ultrasonography, Prenatal; D014597:Uterine Rupture / Q000453:epidemiology*; D014599:Uterus / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D016064:Vaginal Birth after Cesarean
keywords: lower uterine segment; uterine rupture; vaginal birth after cesarean delivery