title: Normal Range of Fetal Nasal Bone Length during the Second Trimester in an Afro-Caribbean Population and Likelihood Ratio for Trisomy 21 of Absent or Hypoplastic Nasal Bone.
abstract: OBJECTIVE
  To establish the normal reference range of fetal nasal bone length (NBL) during the second trimester in an Afro-Caribbean population and the likelihood ratio (LR) for fetal trisomy 21.
  
  
  METHODS
  Prenatal records of euploid, non-malformed singleton fetuses who underwent second-trimester ultrasonographic scans at 20-24 weeks of gestation were retrospectively analyzed for NBL and gestational age (GA). Only Afro-Caribbean couples were selected. The relationship between fetal NBL and GA was determined. The data of all fetuses with Down syndrome were provided by the French West Indies Register of Congenital Malformations (REMALAN).
  
  
  RESULTS
  There was a significant linear association between fetal NBL and GA (R2 = 0. 354). The 50th percentile for NBL increased from 5.0 to 7.0 mm from week 20 to 24 of gestation. The nasal bone (NB) was absent or hypoplastic in 8.6% of the euploid fetuses and in 69.2% of the trisomy 21 fetuses. The LR for trisomy 21 of absent or hypoplastic NB in an Afro-Caribbean population was 8.02, but only 2.32 when this sign was isolated.
  
  
  CONCLUSIONS
  The reference range for fetal NBL at 20-24 weeks of gestation in an Afro-Caribbean population and the LR for trisomy 21 of absent or hypoplastic NB differed from the other populations.
authors.affiliation: Multidisciplinary Center of Prenatal Diagnosis of Martinique, University Hospital of Martinique, Fort de France, France.
authors.forename: Manuella
authors.initials: M
authors.lastname: Gautier
authors.forename: Michèle
authors.initials: M
authors.lastname: Gueneret
authors.forename: Corinne
authors.initials: C
authors.lastname: Plavonil
authors.forename: Eugénie
authors.initials: E
authors.lastname: Jolivet
authors.forename: Bruno
authors.initials: B
authors.lastname: Schaub
mesh_terms: D004314:Down Syndrome / Q000000981:diagnostic imaging*; D005260:Female; D005865:Gestational Age; D006801:Humans; D008395:Martinique; D009295:Nasal Bone / Q000000981:diagnostic imaging*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012016:Reference Values; D012189:Retrospective Studies; D016216:Ultrasonography, Prenatal
keywords: Afro-Caribbean population; Down syndrome; Fetal nasal bone; Likelihood ratio; Normal range; Second trimester; Trisomy 21; Ultrasound