title: Evaluation of the adequacy of reference charts for the accurate identification of fetuses with bone length below the 5th percentile.
abstract: OBJECTIVE
  To identify reference charts for femoral and humeral lengths enabling appropriate identification of fetuses <5th percentile in one population.
  
  
  METHODS
  Two samples of fetuses aged 14-40 weeks were selected from our institution's ultrasonographic database. Regression analysis was used to construct reference charts of femoral and humeral lengths based on the local population (n=901). Femur and humerus length measurements from a second sample (n=1240) were transformed into Z-scores using local and previously published equations. Z-score distributions were used to assess the appropriateness of reference curves for our population. Fetuses aged 18-24 weeks with measurements <5th percentile were identified using each reference equation.
  
  
  RESULTS
  For femoral length, one equation other than the local equation yielded Z-score values within the standard normal distribution (P=0.10), but the histogram was skewed to the right. All Z-score distributions for humeral length fell within the normal distribution (P>0.05), but one was skewed to the right. The numbers of fetuses with femoral and humeral lengths <5th percentile in second-trimester ultrasound examinations varied widely among reference equations used.
  
  
  CONCLUSIONS
  Most reference charts assessed underestimated the number of fetuses with long bone lengths <5th percentile in second-trimester ultrasound examinations and were thus unfit for interpretations of biometric data from the study population.
authors.forename: Ana Alice Vidal
authors.initials: AA
authors.lastname: de Carvalho
authors.forename: José Antônio
authors.initials: JA
authors.lastname: Carvalho
authors.forename: Israel
authors.identifier: http://orcid.org/0000-0002-2054-0739
authors.initials: I
authors.lastname: Figueiredo
authors.forename: Luis Guillermo
authors.initials: LG
authors.lastname: Velarde
authors.forename: Edson
authors.initials: E
authors.lastname: Marchiori
mesh_terms: D000328:Adult; D001699:Biometry; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D005333:Fetus / Q000000981:diagnostic imaging*; D005865:Gestational Age; D006801:Humans; D006811:Humerus / Q000000981:diagnostic imaging; D011247:Pregnancy; D012016:Reference Values; D012044:Regression Analysis; D012189:Retrospective Studies; D016216:Ultrasonography, Prenatal