Benacerraf et al developed a sonographic scoring index, which can help identify a second trimester fetus with an autosomal trisomy. The authors are from Massachusetts General Hospital in Boston.
(1) nuchal fold thickness (not nuchal lucency)
(2) ratio of observed to expected femur length
(3) ratio of observed to expected humerus length
(4) major abnormality (hydrocephalus, heart defect, limb defect, etc)
(6) choroids plexus cysts
(7) hyperechoic bowel
nuchal fold thickness
< 6 mm
>= 6 mm
ratio of observed to expected femur length
< 0.92 (shorter than expected)
ratio of observed to expected humerus length
< 0.90 (shorter than expected)
choroid plexus cyst
• Nuchal fold thickness was measured from the outer aspect of the occipital bone to the skin edge.
• Pyeloectasis is when the anteroposterior diameter of the renal pelvis is >= 4 mm.
• Choroid plexus cysts are indicated by the presence of anechoic areas within the substance of the fetal choroids plexus.
• Hyperechoic bowel has the same or more echogenic compared to bone.
total index =
= SUM(points for all 7 parameters)
• minimum index: 0
• maximum index: 9
• A positive index was >= 2, with the fetus referred for amniocentesis.
• The sensitivity at the cutoff for all trisomies was 77% and the specificity 96%.
• The Youden score for a cutoff of >= 1 was similar (sensitivity 82% and specificity 90%).
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Purpose: To evaluate a second trimester fetus for possible signs of an autosomal trisomy using the sonographic scoring index of Benacerraf et al.
Specialty: Obstetrics & Gynecology, Pedatrics, Genetics
Objective: imaging studies, severity, prognosis, stage