title: Ultrasonographic estimate of birth weight at 24 to 34 weeks: a multicenter study.
abstract: OBJECTIVE
  The study was intended to compare the accuracies of ultrasonographic estimates of birth weights among infants born between 24 and 34 weeks' gestation at 3 tertiary centers.
  
  
  METHODS
  In this retrospective study subjects were matched for gestational age (1:1); all underwent ultrasonographic examination within 2 weeks of delivery. The estimates of birth weight were obtained according to 26 published regression equations and their accuracies were assessed with the mean standardized absolute error. For each center the equation with the lowest error was selected to generate (1) receiver-operating characteristic curves for an estimate to identify actual weight < 1500 g and (2) prediction limit calculations to determine the estimate that ensures at 70% confidence a birth weight > 1500 g.
  
  
  RESULTS
  One hundred seventy-one cases were analyzed at each center. Comparison of the 26 mean standardized errors at each center indicated that (1) the range was rather wide (eg, 89 +/- 87 to 365 +/- 313 g/kg) and (2) 73% (19/26) of the equations had significantly (P < .05) different accuracies. Receiver-operator characteristic curves show that fetal weight estimates of > or = 1600 g at 2 centers and > or = 1700 g at the third center are required to predict actual birth weight < 1500 g. Prediction limit calculation suggests that different fetal weight estimates (> 1600 g at center 1, > 1900 g for the center II, and > 1800 g at center III) are needed to predict actual weight > 1500 g with a 70% accuracy.
  
  
  CONCLUSIONS
  Ultrasonographic estimates of weight for preterm infants, as obtained from 26 equations, are characterized by a rather wide range of accuracy; for most of the equations the accuracies of estimates differ markedly among centers.
authors.affiliation: Department of Obstetrics and Gynecology at Medical College of Georgia, Atlanta, USA.
authors.forename: S P
authors.initials: SP
authors.lastname: Chauhan
authors.forename: S F
authors.initials: SF
authors.lastname: Charania
authors.forename: R A
authors.initials: RA
authors.lastname: McLaren
authors.forename: L D
authors.initials: LD
authors.lastname: Devoe
authors.forename: E L
authors.initials: EL
authors.lastname: Ross
authors.forename: N W
authors.initials: NW
authors.lastname: Hendrix
authors.forename: J C
authors.initials: JC
authors.lastname: Morrison
mesh_terms: D001724:Birth Weight; D005189:False Positive Reactions; D005260:Female; D005865:Gestational Age; D006801:Humans; D007752:Obstetric Labor, Premature; D011247:Pregnancy; D012372:ROC Curve; D012044:Regression Analysis; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal