title: Specific formulas improve the estimation of fetal weight by ultrasound scan.
abstract: OBJECTIVE
  To develop and evaluate local, sex specific, small for gestational age (SGA) specific, large for gestational age (LGA) specific and combined (biometry, sex and Doppler indices) formulas for ultrasound estimated fetal weight (EFW).
  
  
  METHODS
  Low-risk singleton pregnancies that delivered within 7 days from ultrasound examination were assessed. A formula-generating group (1407 pregnancies) and a validation group (469 pregnancies) were created. Fractional regression analysis was used to develop the formulas. Systematic error, random error, fraction within the 10% of actual birth weight and Bland-Altman analysis were used.
  
  
  RESULTS
  The local formula and the Hadlock formula with local co-efficients performed better than the Hadlock formula. The SGA-specific formula, the LGA-specific formula and the combined formula had the lower systematic error (MSE: +0.0022291, -0.4226888, +0.8386222, respectively) and the narrower 95% LOA (-292.8 to +292.23, -485.6 to +461.5, -425.7 to +450.46, respectively). The SGA- and the LGA-specific formulas had higher fraction within the 10% of actual birth weight (81.5% and 84%, respectively).
  
  
  CONCLUSIONS
  Local formulas improve the EFW calculation. The combined formula can further optimize the accuracy and precision. Application of specific formulas for the small and the large fetus had the most pronounced effect in improving fetal weight estimation.
authors: Fetal Medicine Unit, 3rd Department of Obstetrics and Gynaecology, University of Athens, Attikon University Hospital , Athens , Greece and.
authors: Athena P
authors: AP
authors: Souka
authors: Ioannis
authors: I
authors: Papastefanou
authors: Vasiliki
authors: V
authors: Michalitsi
authors: Athanasios
authors: A
authors: Pilalis
authors: Dimitrios
authors: D
authors: Kassanos
mesh_terms: D000465:Algorithms; D000886:Anthropometry; D005260:Female; D020567:Fetal Weight; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D012044:Regression Analysis; D016216:Ultrasonography, Prenatal