title: Fetal nuchal fold thickness measurement between 18 and 24 weeks of pregnancy: reference intervals for a Brazilian population.
abstract: OBJECTIVE
  To determine reference intervals of fetal nuchal fold (NF) thickness measurement in the second trimester of pregnancy in a Brazilian population.
  
  
  METHODS
  This was a retrospective cross-sectional study with 2559 normal singleton pregnancies between 18 and 24 weeks of pregnancy. The fetal NF was obtained in the axial plane of fetal head at level of lateral ventricles including the cavum septum pellucidum, third ventricle, thalamus and transverse cerebellar diameter. The NF was measured posterior to the occipital bone, from the bone surface to the skin, including only soft tissue. To assess the correlation between fetal NF and gestational age (GA), polynomial equations were calculated and adjusted to determination coefficient (R(2)).
  
  
  RESULTS
  The mean fetal NF ranged from 3.98 ± 1.14 mm at 18-18+6 to 4.83 ± 0.93 mm at 24-24+6 weeks of gestation. A good correlation was observed between fetal NF and GA, which is better represented by a linear equation: NF=1.055+0.158*GA (R(2) =0.06).
  
  
  CONCLUSIONS
  Reference intervals of fetal NF thickness measurement in the second trimester of pregnancy were determined for a Brazilian population.
authors.affiliation: Referral Center for Teaching of Diagnostic Imaging (CETRUS) , São Paulo-SP , Brazil .
authors.forename: Edward
authors.initials: E
authors.lastname: Araujo Júnior
authors.forename: Wellington P
authors.initials: WP
authors.lastname: Martins
authors.forename: Claudio Rodrigues
authors.initials: CR
authors.lastname: Pires
authors.forename: Eduardo Félix Martins
authors.initials: EF
authors.lastname: Santana
authors.forename: Sebastião
authors.initials: S
authors.lastname: Zanforlin Filho
mesh_terms: D000293:Adolescent; D000328:Adult; D001938:Brazil / Q000453:epidemiology; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D008875:Middle Aged; D048208:Nuchal Translucency Measurement / Q000592:standards / Q000706:statistics & numerical data; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012016:Reference Values; D012189:Retrospective Studies; D016216:Ultrasonography, Prenatal / Q000592:standards; D055815:Young Adult
keywords: Brazilian population; fetus; nuchal fold thickness; reference intervals