title: Prenasal thickness to nasal bone length ratio in normal and trisomy 21 fetuses at 11-14 weeks of gestation.
abstract: OBJECTIVE
  To show the feasibility and to create a reference range for prenasal thickness (PT) and for the PT to nasal bone length (NBL) ratio in normal fetuses at 11-14 gestational weeks and to compare the findings to fetuses with trisomy 21.
  
  
  METHODS
  PT, NBL and PT/NBL ratio were measured retrospectively in stored two-dimensional images of 1155 normal fetuses and 44 fetuses with trisomy 21. Mid-sagittal images were acquired at first trimester ultrasound examinations and were selected from our digital database.
  
  
  RESULTS
  The PT increased with CRL from 1.0 mm at 45-mm CRL to 1.6 mm at 84-mm CRL. The mean PT/NBL ratio was 0.6 and was not altered by CRL. The mean PT/NBL ratio in fetuses with trisomy 21 was significantly higher than in normal fetuses (p < 0.0001). For a cut-off value of 0.8 the PT/NBL yielded a sensitivity of 86.4% and a specificity of 98.4% for trisomy 21.
  
  
  CONCLUSIONS
  The assessment of PT between 11 and 14 gestational weeks is feasible with high intraclass correlation. The PT to NBL ratio seems to be a promising marker for trisomy 21 in the first trimester and was superior to the isolated contribution of NBL and PT measurements.
authors.affiliation: University of Bonn, Department of Obstetrics and Prenatal Medicine, Germany.|University of Basel, Department of Prenatal Medicine and Gynecologic Ultrasound, Switzerland.
authors.forename: Gwendolin
authors.initials: G
authors.lastname: Manegold-Brauer
authors.affiliation: University of Bonn, Department of Obstetrics and Prenatal Medicine, Germany.
authors.forename: Lucas
authors.initials: L
authors.lastname: Bourdil
authors.affiliation: University of Bonn, Department of Obstetrics and Prenatal Medicine, Germany.|University of Cologne, Division of Prenatal Medicine and Gynecologic Ultrasound, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Berg
authors.affiliation: University of Basel, Department of Biomedicine, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schoetzau
authors.affiliation: University of Bonn, Department of Obstetrics and Prenatal Medicine, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Gembruch
authors.affiliation: University of Bonn, Department of Obstetrics and Prenatal Medicine, Germany.
authors.forename: Annegret
authors.initials: A
authors.lastname: Geipel
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D004314:Down Syndrome / Q000000981:diagnostic imaging*; D005145:Face / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D009295:Nasal Bone / Q000000981:diagnostic imaging*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D012016:Reference Values; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal; D055815:Young Adult