Ultrasound screening of fetuses at increased risk for Down syndrome: How many missed diagnoses?

Aaron B. Caughey, Deirdre J. Lyell, A. Eugene Washington, Roy A. Filly, Mary E. Norton

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Objective: To determine the number of Down syndrome (DS) fetuses identified, amniocenteses performed, and procedure-related losses incurred when second-trimester ultrasound is used to screen high-risk patients in order to determine who should undergo an amniocentesis. Methods: A decision analytic model was designed for women at increased risk for a DS fetus due to either advanced maternal age (AMA) or a positive expanded maternal serum alpha fetoprotein (MSAFP) screening test, also known as a triple screen (+triple) test. The model compared: (1) the current standard of offering all at-risk women amniocentesis to (2) a policy of performing amniocentesis only when sonographic markers of DS are seen on ultrasound. Baseline assumptions included a sensitivity of 60.6% for targeted ultrasound and a screen-positive rate of 16.2%. Results: If targeted ultrasound is used to determine whether high-risk patients should undergo amniocentesis, 56% (3933/7025) of all DS fetuses are missed. The diagnosis of DS is missed most frequently among women at highest risk for DS (AMA and +triple). In this subgroup of patients, there are 3152 DS fetuses in the second trimester, of which 2815 (89%) are identified by triple screen test. When an ultrasound screen is added, only 1709 (54%) of DS fetuses will be identified. Conclusion: Substantially fewer DS fetuses will be detected when targeted ultrasound is used as a screen among already identified high-risk patients.

Original languageEnglish (US)
Pages (from-to)22-27
Number of pages6
JournalPrenatal Diagnosis
Issue number1
StatePublished - Jan 2006
Externally publishedYes


  • Down syndrome
  • Prenatal diagnosis
  • Ultrasound

ASJC Scopus subject areas

  • Obstetrics and Gynecology
  • Genetics(clinical)


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