title: Ultrasonographic evaluation of fetal nasal bone in a low-risk population at 11-13 + 6 gestational weeks.
abstract: OBJECTIVE
  To evaluate the utility of determining the presence/absence of nasal bone in a low-risk fetal population.
  
  
  METHODS
  Prospective study of the presence/absence of nasal bone among 1800 consecutive unselected fetuses, with complete follow-up of results.
  
  
  RESULTS
  An adequate sonographic evaluation of nasal bone was obtained in 1682 (93.44%) of the fetuses. Nasal bone was considered absent in 19 (1.06%) of 1790 fetuses with a normal karyotype and in 2 (28.57%) of the seven recorded cases of Down syndrome (DS). The overall first-trimester sensitivity for DS to the absence of nasal bone was two of the six cases (33.3%) and the false-positive rate was 1.13%. The positive predictive value for DS of the absence of nasal bone was 2/21 (9.52%).
  
  
  CONCLUSIONS
  In a low-risk population, the evaluation of the presence/absence of nasal bone in DS screening during the first trimester has a low sensitivity. First-trimester assessment of the nasal bone in population screening may play a lesser role than in the re-evaluation of high-risk pregnancies.
authors.affiliation: Servicio de Obstetricia y Ginecología, Hospital Universitario V. Macarena, Sevilla, Spain. ramoscor@arrakis.es
authors.forename: Domingo
authors.initials: D
authors.lastname: Ramos-Corpas
authors.forename: Juan C
authors.initials: JC
authors.lastname: Santiago
authors.forename: Francisco
authors.initials: F
authors.lastname: Montoya
mesh_terms: D000293:Adolescent; D000328:Adult; D004314:Down Syndrome / Q000175:diagnosis* / Q000196:embryology / Q000453:epidemiology; D005189:False Positive Reactions; D005260:Female; D047109:Fetal Development; D005500:Follow-Up Studies; D005865:Gestational Age; D006801:Humans; D008875:Middle Aged; D009295:Nasal Bone / Q000000981:diagnostic imaging* / Q000196:embryology*; D011247:Pregnancy; D011446:Prospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013030:Spain / Q000453:epidemiology; D016216:Ultrasonography, Prenatal