title: First-trimester nasal bone length in a normal Latin American population.
abstract: OBJECTIVE
  To report normative data of nasal bone length (NBL) in first-trimester singleton fetuses in a normal cohort of Latin American women.
  
  
  METHODS
  NBL was measured during routine first-trimester sonographic examination in 1040 singleton fetuses from an unselected population.
  
  
  RESULTS
  NBL increased linearly with advancing gestational age (GA) [NBL (mm) = - 1.10 + 0.03 x GA (days), R(2) = 0.21; p < 0.001]. Similarly, there was a linear relationship between the NBL and crown-lump length (CRL) [NBL (mm) = 0.41 + 0.02 x CRL (mm), R(2) = 0.27; p < 0.001]. The NBLs at the 50th percentile in our population were 1.5, 1.7, and 1.9 mm at 11, 12, and 13 weeks of gestation, respectively.
  
  
  CONCLUSIONS
  Whereas categorizing a nasal bone as absent or present can be subjective because of variations in echogenicity due to technique and equipment, measurement of NBL is a more objective approach to nasal bone assessment in screening for aneuploidy. Measurement of NBL in the first trimester is feasible and can be easily obtained at the time of nuchal translucency assessment. The normative data we report can provide a reference for defining nasal bone hypoplasia in the first trimester in the Latin American population.
authors.affiliation: Fetal Medicine Center, Department of Obstetrics and Gynecology, Clinica Las Condes, Santiago, Chile.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Casasbuenas
authors.forename: Amy E
authors.initials: AE
authors.lastname: Wong
authors.forename: Waldo
authors.initials: W
authors.lastname: Sepulveda
mesh_terms: D002677:Chile; D015331:Cohort Studies; D005260:Female; D006801:Humans; D009295:Nasal Bone / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D049451:Nomograms; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D016216:Ultrasonography, Prenatal / Q000379:methods