title: A New Sonographic Weight Estimation Formula for Small-for-Gestational-Age Fetuses.
abstract: OBJECTIVE
  The purpose of this study was to develop a new specific weight estimation formula for small-for-gestational-age (SGA) fetuses that differentiated between symmetric and asymmetric growth patterns.
  
  
  METHODS
  A statistical estimation technique known as component-wise gradient boosting was applied to a group of 898 SGA fetuses (symmetric, n = 750; asymmetric, n = 148). A new formula was derived from the data obtained and was then compared to other commonly used equations.
  
  
  RESULTS
  The new formula derived is as follows: estimated fetal weight = e^[1.3734627 + 0.0057133 × biparietal diameter + 0.0011282 × head circumference + 0.0201147 × abdominal circumference + 0.0183081 × femur length - 0.0000177 × biparietal diameter(2) - 0.0000018 × head circumference(2) - 0.0000297 × abdominal circumference(2) -0.0001007 × femur length(2) + 0.0397563 × I(sex = male) + 0.0064505 × gestational age (days) + 0.0096528 × I(SGA = asymmetric)], where the function I denotes an indicator function, which is 1 if the expression is fulfilled (sex = male; SGA type = asymmetric) and otherwise 0. In the whole study group and the 2 subgroups, the new formula showed the lowest median absolute percentage error, mean percentage error, and random error and the best distribution of absolute percentage errors within prespecified error bounds.
  
  
  CONCLUSIONS
  The new formula substantially improves weight estimation in SGA fetuses.
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital of Erlangen, Erlangen, Germany florian.faschingbauer@uk-erlangen.de.
authors.forename: Florian
authors.initials: F
authors.lastname: Faschingbauer
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital of Erlangen, Erlangen, Germany.
authors.forename: Ulf
authors.initials: U
authors.lastname: Dammer
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital of Erlangen, Erlangen, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Raabe
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital of Erlangen, Erlangen, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Kehl
authors.affiliation: Department of Medical Informatics, Biometry, and Epidemiology, Rheinische Friedrich-Wilhelms-University of Bonn, Bonn, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Schmid
authors.affiliation: Department of Obstetrics and Perinatal Medicine, Diakonischen Dienste Hanover Frauenkliniken, Hanover, Germany.
authors.forename: Ralf L
authors.initials: RL
authors.lastname: Schild
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital of Erlangen, Erlangen, Germany.
authors.forename: Matthias W
authors.initials: MW
authors.lastname: Beckmann
authors.affiliation: Department of Medical Informatics, Biometry, and Epidemiology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Mayr
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D020567:Fetal Weight / Q000502:physiology*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age / Q000502:physiology*; D008297:Male; D011247:Pregnancy; D012189:Retrospective Studies; D016216:Ultrasonography, Prenatal / Q000379:methods*
keywords: birth weight; fetal weight estimation; new regression formula; obstetric ultrasound; small for gestational age; sonography