title: Prediction of fetal macrosomia: effect of sonographic fetal weight-estimation model and threshold used.
abstract: OBJECTIVE
  To compare the accuracy of 21 sonographic fetal weight-estimation models and abdominal circumference (AC) as a single measure for the prediction of fetal macrosomia (> 4000 g) using either fixed or optimal model-specific thresholds.
  
  
  METHODS
  A total of 4765 sonographic weight estimations performed within 3 days prior to delivery were analyzed. The predictive accuracy of 21 published sonographic fetal weight-estimation models was calculated using three different thresholds: a fixed threshold of 4000 g; a model-specific threshold obtained from the inflexion point of the receiver-operating characteristics (ROC) curve; and a model-specific threshold associated with the highest overall accuracy. Cluster analysis was used to determine whether a certain combination of fetal biometric indices is associated with a higher predictive accuracy than others.
  
  
  RESULTS
  For a fixed threshold of > 4000 g, there was considerable variation among the models in sensitivity (range, 13.6-98.5%) and specificity (range, 63.6-99.8%) for fetal macrosomia. Use of the threshold derived from the inflexion point of the ROC curve decreased the intermodel variation to a minimum (sensitivity, 84.4-91.4%; and specificity, 79.5-86.3%). Even when this optimal model-specific threshold was applied, models based on three to four biometric indices were more accurate than were models based on only two biometric indices or on AC as a single measure (P=0.03).
  
  
  CONCLUSIONS
  Sonographic fetal weight-estimation models based on three to four biometric indices appear to be more accurate than are models based on two indices or on AC as a single measure, for the diagnosis of macrosomia. In these cases, the use of an optimal, model-specific threshold is associated with a higher degree of accuracy than is the uniform use of a fixed threshold of an estimated weight of > 4000 g.
authors.affiliation: Helen Schneider Hospital for Women, Rabin Medical Center, Petah Tiqva, and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. nirm@clalit.org.il
authors.forename: N
authors.initials: N
authors.lastname: Melamed
authors.forename: Y
authors.initials: Y
authors.lastname: Yogev
authors.forename: I
authors.initials: I
authors.lastname: Meizner
authors.forename: R
authors.initials: R
authors.lastname: Mashiach
authors.forename: J
authors.initials: J
authors.lastname: Pardo
authors.forename: A
authors.initials: A
authors.lastname: Ben-Haroush
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging* / Q000196:embryology; D000328:Adult; D001699:Biometry / Q000379:methods; D016000:Cluster Analysis; D005260:Female; D005320:Fetal Macrosomia / Q000000981:diagnostic imaging*; D020567:Fetal Weight / Q000502:physiology*; D005865:Gestational Age; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal / Q000379:methods* / Q000592:standards