title: Measurement of fetal nasal width by ultrasonography.
abstract: OBJECTIVE
  This study was designed to determine the range of normal fetal nasal width by ultrasonography, which may be beneficial for detection of trisomy 21 and other chromosomal abnormalities. We hypothesize that a wide, saddle-shaped nose, which is one of the clinical neonatal anatomic features of trisomy 21, can be diagnosed prenatally.
  
  
  METHODS
  Fetal nasal width diameter was measured on 782 normal white fetuses by ultrasonography. Gestational ages ranged from 13.8 to 40.4 weeks. Mean and SD of fetal width diameter was calculated weekly by gestational age to establish normal values.
  
  
  RESULTS
  The fetal nasal width increased as a function of gestational age, showing a polynomial curve during pregnancy (r = 0.912, p = 0.002). With use of mean +/- 1 SD as a cutoff value, the results showed a sensitivity of 80% with a specificity of 67% and a positive predictive value of 2.2% with a negative predictive value of 99.7% for the diagnosis of trisomy 21.
  
  
  CONCLUSIONS
  The fetal nasal width diameter may be used as a biometric measurement and may be useful to identify trisomy 21 or other chromosomal abnormalities in conjunction with other already defined parameters used in a genetic ultrasonographic screen.
authors.affiliation: Department of Obstetrics and Gynecology, Maine Medical Center, Scarborough 04074, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Pinette
authors.forename: J
authors.initials: J
authors.lastname: Blackstone
authors.forename: Y
authors.initials: Y
authors.lastname: Pan
authors.forename: S G
authors.initials: SG
authors.lastname: Pinette
mesh_terms: D000649:Amniocentesis; D004314:Down Syndrome / Q000175:diagnosis / Q000000981:diagnostic imaging; D005260:Female; D005865:Gestational Age; D006801:Humans; D007621:Karyotyping; D009666:Nose / Q000000981:diagnostic imaging* / Q000196:embryology*; D011247:Pregnancy; D012016:Reference Values; D016216:Ultrasonography, Prenatal