Fetal nasal bone length: Reference range and clinical application in ultrasound screening for trisomy 21

V. Bunduki, R. Ruano, J. Miguelez, C. T. Yoshizaki, S. Kahhale, M. Zugaib

Research output: Contribution to journalArticlepeer-review

90 Scopus citations


Objectives: Fetuses with trisomy 21 typically present with subtle facial abnormalities, including a hypoplastic nasal bone. The aim of this study was to provide a reference range for the length of the fetal nasal bone and to test its value in second-trimester ultrasound screening for trisomy 21. Design: A reference range of fetal nasal booze length was established from cross-sectional data on 1923 consecutive singleton pregnancies scanned at 16-24 weeks' gestation in women older than 35 years. Screening for trisomy 21 was prospectively studied using the measurement o f fetal nasal bone lengths smaller than the 5th percentile as a cut-off value. Results: Follow-up was possible in 1631 cases (84.8%). Trisomy 21 was found in 22 cases (1.35%). Nasal bone length measurement increased as a function of gestational age (P < 0.05) showing a linear relationship. Screening for trisomy 21 using the 5th percentile as a cut-off value resulted in a sensitivity of 59.1% for a 5.1% false-positive rate. The likelihood ratio was 11.6. Conclusion: Screening for trisomy 21 using fetal nasal bone length measurements showed a sensitivity comparable to that of maternal biochemistry for a given false-positive rate of 5%. Association of nasal bone lengths with other sonographic markers, taking into account the background risk for maternal and gestational age, may further improve sensitivity and reduce false positives, allowing avoidance of unnecessary invasive diagnostic procedures.

Original languageEnglish (US)
Pages (from-to)156-160
Number of pages5
JournalUltrasound in Obstetrics and Gynecology
Issue number2
StatePublished - Feb 1 2003


  • Chromosomal abnormalities
  • Fetus
  • Nasal bone
  • Trisomy 21
  • Ultrasound

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Reproductive Medicine
  • Radiology Nuclear Medicine and imaging
  • Obstetrics and Gynecology


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