II. Indications: Non-invasively assess trisomy risk

  1. Maternal age over 35 years

III. 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%

IV. Screening: 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

V. Evaluation: Findings suggestive of Trisomy

  1. Amniocentesis with karyotype

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