title: Sonographic fetal asymmetry predicts shoulder dystocia.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the performance of a sonographic measurement of fetal asymmetry, abdominal diameter minus biparietal diameter (AD - BPD), in the prediction of shoulder dystocia (SD) in a patient population that was unselected for diabetes mellitus (DM) status.
  
  
  METHODS
  Patients who underwent sonographic estimations of fetal biometric measurements within 14 days of vaginally delivered live-born singleton neonates weighing 3400 g or greater at a tertiary care institution were included in this retrospective cohort. The mean AD - BPD was retrospectively compared in deliveries complicated by SD with those without SD by the Student t test. A receiver operating characteristic curve was generated to determine the optimal cutoff for SD prediction. Test performance characteristics of AD - BPD were determined.
  
  
  RESULTS
  Of 5204 deliveries, 332 met inclusion criteria. Shoulder dystocia complicated 23 deliveries (6.9%). The mean AD - BPD was significantly higher in the dystocia group (2.39 versus 1.97; P = .0002). With an AD - BPD of 2.6 cm or greater, the risk rates of SD were 25% for unselected patients and 38.5% with DM.
  
  
  CONCLUSIONS
  An AD - BPD of 2.6 cm or greater identifies a subset of patients with and without DM at risk for SD.
authors.affiliation: Division of Maternal-Fetal Medicine, Columbia University Medical Center, 622 W 168th St, PH 16-66, New York, NY 10032, USA. rsm20@columbia.edu
authors.forename: Russell S
authors.initials: RS
authors.lastname: Miller
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Devine
authors.forename: E Blair
authors.initials: EB
authors.lastname: Johnson
mesh_terms: D000328:Adult; D015331:Cohort Studies; D015897:Comorbidity; D016640:Diabetes, Gestational / Q000453:epidemiology*; D004420:Dystocia / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D015994:Incidence; D009518:New York / Q000453:epidemiology; D011247:Pregnancy; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal / Q000379:methods* / Q000706:statistics & numerical data*