title: Effect of birth weight on adverse obstetric outcomes in vaginal birth after cesarean delivery.
abstract: OBJECTIVE
  To estimate the association between neonatal birth weight and adverse obstetric outcomes in women attempting vaginal birth after cesarean.
  
  
  METHODS
  We reviewed the medical records of all women undergoing a trial of labor after a prior low transverse cesarean delivery in our institution between 1987 and 2004. Patients were categorized according to birth weight (less than 3,500 g [group 1, reference], 3,500-3,999 g [group 2], and 4,000 g or more [group 3]) and prior vaginal delivery. The rates of failed trial of labor, uterine rupture, shoulder dystocia, and third- and fourth-degree perineal laceration were compared among groups. Multivariable logistic regressions were performed to adjust for potential confounding factors.
  
  
  RESULTS
  Of 2,586 women, 1,519 (59%), 798 (31%), and 269 (10%) were included in groups 1, 2, and 3, respectively. Birth weight was directly correlated to the rate of failed trial of labor (19%, 28%, and 38% for groups 1, 2, and 3, respectively; P<.01), uterine rupture (0.9%, 1.8%, and 2.6%; P<.05), shoulder dystocia (0.3%, 1.6%, and 7.8%; P<.01), and third- and fourth-degree perineal laceration (5%, 7%, and 12%; P<.01). After adjustment for confounding variables, birth weight of 4,000 g or more remained associated with uterine rupture (odds ratio [OR] 2.62, 95% confidence interval [CI] 1.001-6.85), failed trial of labor (OR 2.47, 95% CI 1.82-3.34), shoulder dystocia (OR 25.13, 95% CI 9.31-67.86), and third- and fourth-degree perineal laceration (OR 2.64, 95% CI 1.66-4.19).
  
  
  CONCLUSIONS
  Birth weight and specifically macrosomia are linked with failed trial of labor, uterine rupture, shoulder dystocia, and third- and fourth-degree perineal laceration in women who underwent prior cesarean delivery. Estimated fetal weight should be included in the decision-making process for all women contemplating a trial of labor after cesarean delivery.
  
  
  METHODS
  II.
authors.affiliation: From the Department of Obstetrics and Gynaecology, Faculty of Medicine, Hôpital Sainte-Justine, Université de Montréal, Montréal, Québec, Canada; and Department of Obstetrics and Gynaecology, Faculty of Medicine, Centre de recherche du Centre hospitalier universitaire de Québec, Université Laval, Québec, Québec, Canada.
authors.forename: Nicole
authors.initials: N
authors.lastname: Jastrow
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Roberge
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gauthier
authors.forename: Liny
authors.initials: L
authors.lastname: Laroche
authors.forename: Louise
authors.initials: L
authors.lastname: Duperron
authors.forename: Normand
authors.initials: N
authors.lastname: Brassard
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Bujold
mesh_terms: D000328:Adult; D001724:Birth Weight; D004420:Dystocia / Q000209:etiology; D005260:Female; D005320:Fetal Macrosomia; D006801:Humans; D007231:Infant, Newborn; D010502:Perineum / Q000293:injuries; D011247:Pregnancy; D014219:Trial of Labor; D014597:Uterine Rupture / Q000209:etiology; D016064:Vaginal Birth after Cesarean / Q000009:adverse effects*