Second Trimester Sonogram for evaluation of Soft Marker Screening for chromosomal abnormalities

Second Trimester Sonogram for evaluation of Soft Marker Screening for chromosomal abnormalities

High-level markers:

    - Non ossified Nasal Bone (LR= 6.6)


Mid-level markers:

    - Nuchal skin fold (LR= 3.8)
  
    - Cerebral ventriculomegaly (LR= 3.8)
  
    - ARSA (Aberrant Right Subclavian Artery) (LR= 3.9)


Low-level markers:

    - Echogenic bowel foci (LR= 1.6)

    - Mild pyelectasis (LR= 1.1)


Soft Markers and Risk Assessment

It is important to realize that none of the soft markers for Down syndrome are abnormalities. 

The way that most of these markers were determined is by reviewing either images or videotapes from ultrasound scans done of both normal babies and babies with Down syndrome. 

If a certain percentage of normal babies carries one of these markers, but a higher percentage of Down syndrome pregnancies carries a marker, then the marker can be used to statistically adjust the Down syndrome risk calculation.


Overall, about 7 percent of pregnancies will show a soft marker increasing the risk calculation for Down syndrome.

About 93 percent of pregnancies will show no soft markers, and when no soft markers are seen, the Down syndrome risk calculation is lowered. 

We multiply the risk calculation by a factor of 0.4, so that if the risk calculation was 1 per 1,000, and no soft markers are seen, then our final risk calculation would be 0.4 per 1,000.

Soft Marker Screening for Edaward Syndrome

Mid-level markers:

    - Choroid plexus cysts   (LR=7-10)