title: Frequent epidural dosing as a marker for impending uterine rupture in patients who attempt vaginal birth after cesarean delivery.
abstract: OBJECTIVE
  The purpose of this study was to estimate the association between epidural dosing and the risk of uterine rupture in women who attempt vaginal birth after cesarean delivery (VBAC).
  
  
  METHODS
  A nested case-control study within a multicenter retrospective cohort of >25,000 women with previous cesarean delivery compared cases of uterine rupture with women without rupture (control subjects) while attempting VBAC with epidural anesthesia. Dose timing, frequency, and quantity were compared. Time-to-event analyses were performed to estimate the association between epidural dosing and risk for uterine rupture while accounting for labor duration.
  
  
  RESULTS
  Of 804 women in the nested case-control study, 504 women (62.7%) had epidural anesthesia, with no statistical difference in epidural usage rates between cases and control subjects (70.4% vs 62.4%; P = .09). Cox-regression analysis revealed a dose-response relationship between the number of epidural doses and uterine rupture risk: 1 dose (hazard ratio, 2.8; 95% confidence interval [CI], 1.4-5.7), 2 doses (hazard ratio, 3.1; 95% CI, 2.2-6.2), 3 doses (hazard ratio, 6.7; 95% CI, 3.8-12.1), > or =4 doses (hazard ratio, 8.1; 95% CI, 5.4-18.2).
  
  
  CONCLUSIONS
  Clinical suspicion for uterine rupture should be high in women who require frequent epidural dosing during a VBAC trial.
authors.affiliation: Department of Obstetrics and Gynecology, Washington University in St. Louis School of Medicine, St. Louis, MO, USA.
authors.forename: Alison G
authors.initials: AG
authors.lastname: Cahill
authors.forename: Anthony O
authors.initials: AO
authors.lastname: Odibo
authors.forename: Jenifer E
authors.initials: JE
authors.lastname: Allsworth
authors.forename: George A
authors.initials: GA
authors.lastname: Macones
mesh_terms: D000328:Adult; D000767:Anesthesia, Epidural / Q000706:statistics & numerical data*; D000773:Anesthesia, Obstetrical / Q000706:statistics & numerical data*; D016022:Case-Control Studies; D002585:Cesarean Section / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D011237:Predictive Value of Tests; D011247:Pregnancy; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors; D014597:Uterine Rupture / Q000175:diagnosis* / Q000453:epidemiology*; D016064:Vaginal Birth after Cesarean / Q000706:statistics & numerical data*