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Trisomy Findings on Fetal Ultrasound

Indications: non-invasively assess trisomy risk
1. Maternal age over 35 years
General
1. Trisomy risk Age >35 years
  1. Overall: 1 in 80
  2. With Negative Ultrasound: 1 in 400
2. Ultrasound detects
  1. Trisomy 18: 100%
  2. Trisomy 21: 66%
Rating system to assess for Trisomy
1. Scoring
  1. Nuchal Fold (5mm)
    1. Assess at level of Cerebellum and cisterna magna
    2. Not predictive after 21 weeks
    3. 2 Points
  2. Short femur length
    1. 1 Point
  3. Cystic Hygroma
    1. Seen in Turners Syndrome, Trisomy 21, Idiopathic
    2. 1 Point
  4. Septal defect or other heart defect
    1. 1 Point
  5. Choroid plexus cyst
    1. 1 Point
2. Interpretation: Score associated with Trisomy risk
  1. Age <35: Score >= 2 points
  2. Age >35: Score >= 1 point
Management: Findings suggestive of Trisomy
1. Amniocentesis with karyotype

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This page was written by Scott Moses, MD. This page was last revised before 5/10/08, prior to consistent tracking of revision date. This page was last published on 6/1/2008. Please send comments and questions to the editor. Contact information may be found on the page About the Family Practice Notebook. These pages are best viewed with Microsoft Internet Explorer 6.0.