title: Prediction of cesarean delivery using the fetal-pelvic index.
abstract: OBJECTIVE
  The purpose of this study was to estimate the usefulness of the fetal-pelvic index (FPI) in the prediction of cesarean delivery among nulliparous and women who undergo a trial of labor after cesarean delivery (TOLAC).
  
  
  METHODS
  This prospective cohort study included subjects at 2 hospitals from the University of Pennsylvania Health system. The study sample included nulliparous women and women who attempted TOLAC, with nonanomalous pregnancies at ≥37 weeks of gestation in vertex presentation (n = 221 and 207, respectively). FPI score was calculated with the ultrasound-based fetal biometric measures that were performed within 2 weeks of delivery and x-ray pelvimetry that was performed within 48 hours of delivery. Multivariable logistic regression was used to develop a clinical predictive index for cesarean delivery, which included FPI and clinical factors, in nulliparous women or women who attempted TOLAC. The prediction models were tested for accuracy with the area under the receiver operating characteristics curve.
  
  
  RESULTS
  Higher FPI scores were associated with greater odds of cesarean delivery. A unit increase in FPI score increased the odds of cesarean delivery by 15% (adjusted odds ratio, 1.15; 95% confidence interval, 1.09-1.21) for nulliparous women and 15% for women who attempted TOLAC (adjusted odds ratio, 1.15; 95% confidence interval, 1.10-1.20) after adjustment for maternal age, race, medical risk factors, and labor method. Among nulliparous women, the receiver operating characteristics analysis estimated an area under the curve of 0.88, with positive and negative predictive values of 76% and 87%, respectively. Similar findings were observed in the subgroup of women who attempted TOLAC.
  
  
  CONCLUSIONS
  The FPI when combined with clinical risk factors can identify accurately women who are at a high risk for cesarean delivery.
authors.affiliation: Department of Obstetrics and Gynecology, Washington University in St. Louis, St. Louis, MO. Electronic address: maconesg@wustl.edu.
authors.forename: George A
authors.initials: GA
authors.lastname: Macones
authors.forename: Jen Jen
authors.initials: JJ
authors.lastname: Chang
authors.forename: David M
authors.initials: DM
authors.lastname: Stamilio
authors.forename: Anthony O
authors.initials: AO
authors.lastname: Odibo
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Alison G
authors.initials: AG
authors.lastname: Cahill
mesh_terms: D000293:Adolescent; D000328:Adult; D002585:Cesarean Section / Q000706:statistics & numerical data*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D015999:Multivariate Analysis; D049451:Nomograms; D016017:Odds Ratio; D010298:Parity; D010384:Pelvic Bones / Q000000981:diagnostic imaging*; D010387:Pelvimetry; D011247:Pregnancy; D011446:Prospective Studies; D012372:ROC Curve; D011859:Radiography; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D014219:Trial of Labor; D016216:Ultrasonography, Prenatal; D016064:Vaginal Birth after Cesarean / Q000706:statistics & numerical data; D055815:Young Adult
keywords: cesarean delivery; fetal pelvic index; prediction; trial of labor after cesarean delivery