title: Estimation of fetal weight: accuracy of regression models versus accuracy of ultrasound data.
abstract: OBJECTIVE
  To determine the respective importance of equation accuracy and variability in interexaminer measurements in estimation of fetal weight (EFW).
  
  
  METHODS
  The study included 3 samples from three different French maternity hospitals. Sample 1 (6,508 fetuses) was used to compute a new linear regression model estimating fetal weight (FW) from ultrasound measurements. Sample 2, with 705 fetuses, was used to compare the accuracy of the new equation with Hadlock's equation. Sample 3 (1,461 fetuses) was used to assess - from our equation and from Hadlock's - the estimation errors due to the variability of ultrasound measurements recorded by 11 distinct examiners. Accuracy was determined by the signed percent difference (%Diff). Statistical analysis included the F test for correlated variances and comparisons of correlated variances.
  
  
  RESULTS
  The random error of our model is 6.8%, significantly lower (p < 0.01) than Hadlock's which is around 7.4% (8.9% for low FW and 7.4% for high FW). The variability of ultrasound measurements among the different examiners in sample 3 generated a significant variation (p < 0.01) in the random error, ranging from 6.7 to 12.5%. This significant variation was also observed using Hadlock's equation for the same sample (from 7.2 to 12%).
  
  
  CONCLUSIONS
  The accuracy of EFW depends much more on the quality of ultrasound measurements than on the choice of equation. Nevertheless, optimizing the accuracy of EFW (about 6.7-6.8%) imperatively requires standardized data collecting.
authors.affiliation: Dynamique de l'Evolution Humaine, UPR 2147, CNRS, Paris, France. jean-claude.pineau@evolhum.cnrs.fr
authors.forename: J C
authors.initials: JC
authors.lastname: Pineau
authors.forename: G
authors.initials: G
authors.lastname: Grange
authors.forename: B
authors.initials: B
authors.lastname: Kapitaniak
authors.forename: C
authors.initials: C
authors.lastname: Vayssiere
authors.forename: J
authors.initials: J
authors.lastname: Tomikowski
authors.forename: A M
authors.initials: AM
authors.lastname: Guihard-Costa
mesh_terms: D001724:Birth Weight; D020567:Fetal Weight; D005602:France; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D016014:Linear Models; D008954:Models, Biological; D015588:Observer Variation; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal / Q000592:standards