title: The MFMU Cesarean Registry: impact of fetal size on trial of labor success for patients with previous cesarean for dystocia.
abstract: OBJECTIVE
  The purpose of this study was to determine the influence of change in infant birth weight between pregnancies on the outcome of a trial of labor for women whose first cesarean delivery was performed for dystocia.
  
  
  METHODS
  Secondary analysis of 7081 patients with 1 previous cesarean delivery and no other deliveries after 20 weeks' gestation, undergoing a trial of labor with a singleton gestation. Cases were classified as dystocia if the listed indication for the cesarean delivery in the first pregnancy was failed induction, cephalo-pelvic disproportion, failure to progress, or failed forceps or vacuum. Outcomes of the trial of labor were correlated with fetal size relative to birth weight in the initial pregnancy for those women whose initial cesarean delivery was for dystocia and those with other indications.
  
  
  RESULTS
  For the cohort being studied (n = 7081), dystocia was the indication for the first cesarean delivery for 3182 (44.9%). Trial of labor resulted in vaginal delivery for 54% of patients whose first cesarean delivery was performed for dystocia, compared with 67% for those with other indications (P < .01). For those whose first cesarean delivery was for dystocia, trial of labor success was correlated with birth weight differences between the pregnancies, with only 38% delivering vaginally if the trial of labor birth weight exceeded the initial pregnancy birth weight by more than 500 g. Using logistic regression and adjusting for other potential confounding factors, the odds of success decreased by 3.8% for each increase of 100 g in birth weight in the trial of labor relative to the first birth weight.
  
  
  CONCLUSIONS
  For women with previous cesarean delivery for dystocia, increasing birth weight in the subsequent trial of labor relative to the first birth weight diminishes the chances of successful vaginal delivery.
authors.affiliation: Department of Obstetrics and Gynecology, Northwestern University, Chicago, IL, USA.
authors.forename: Alan M
authors.initials: AM
authors.lastname: Peaceman
authors.forename: Rebecca
authors.initials: R
authors.lastname: Gersnoviez
authors.forename: Mark B
authors.initials: MB
authors.lastname: Landon
authors.forename: Catherine Y
authors.initials: CY
authors.lastname: Spong
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Leveno
authors.forename: Michael W
authors.initials: MW
authors.lastname: Varner
authors.forename: Dwight J
authors.initials: DJ
authors.lastname: Rouse
authors.forename: Atef H
authors.initials: AH
authors.lastname: Moawad
authors.forename: Steve N
authors.initials: SN
authors.lastname: Caritis
authors.forename: Margaret
authors.initials: M
authors.lastname: Harper
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Wapner
authors.forename: Yoram
authors.initials: Y
authors.lastname: Sorokin
authors.forename: Menachem
authors.initials: M
authors.lastname: Miodovnik
authors.forename: Marshall
authors.initials: M
authors.lastname: Carpenter
authors.forename: Mary J
authors.initials: MJ
authors.lastname: O'Sullivan
authors.forename: Baha M
authors.initials: BM
authors.lastname: Sibai
authors.forename: Oded
authors.initials: O
authors.lastname: Langer
authors.forename: John M
authors.initials: JM
authors.lastname: Thorp
authors.forename: Susan M
authors.initials: SM
authors.lastname: Ramin
authors.forename: Brian M
authors.initials: BM
authors.lastname: Mercer
mesh_terms: D000328:Adult; D001724:Birth Weight; D015331:Cohort Studies; D004420:Dystocia / Q000628:therapy*; D005260:Female; D006801:Humans; D015999:Multivariate Analysis; D011247:Pregnancy; D012042:Registries; D014219:Trial of Labor; D016064:Vaginal Birth after Cesarean