Soft markers

 Q. Why we the obstetricians need to be aware the significance of  soft markers  which may at times may represent some chromosomal abnormality of foetus. By analysing the soft  markers in USG  we may come to  know about it to get the idea of risk calculation of trisomies by assessing soft markers and when to proceed for CVS / Karyotype to confirm abnormal karyotype of foetus based on number of such soft markers present in a given case  .

Q. 2: What are soft markers?? Soft Markers are normal anatomical variants (not abnormality/defects) as observed on ultrasonography of a fetus that are noteworthy because they increase the risk for underlying fetal aneuploidy.

Q. 3: Does Trisomy 21 (Down syndrome) exhibit some soft markers in USG? Yes.  In fact DS  is the most common karyotypic abnormality in live-born infants (1 per 800 live births) and is a leading cause of mental retardation. Other sonographically detectable aneuploidies include trisomy 13, trisomy 18, monosomy X, and triploidies.

Q. 4: What are the general characteristics of Soft Markers? Those are soft markers are :-
1) nonspecific, often transient 
2) Soft markers may be seen in the normal fetus but have an increased incidence in fetuses with chromosomal abnormalities.
3) Soft Markers provide a noninvasive means by which to adjust the a priori risk on the basis of  presence /Absence of them.

4) Prenatal ultrasonography during the second trimester (15-22wks) provides a “genetic sonogram” which picks up one , many or no soft markers in a given case. Compiling the data along with any . other  morphologic features of fetus –a decesion is done about Amniocentesis to substitute / exclude chromosomal abnormality of foetus. .This includes  Down syndrome as well.

What are the nine important Soft Markers that a sonologists look for ??

1) Nuchal Fold Thickness
2) Mild Ventriculomegaly
3) Aberrant Rt Subclavian A
4) Absent/Hypoplastic Nasal Bone
5) Short Humerus
6) Short Femur
7) Echogenic Intracardiac Focus
8) Echogenic Bowel
9) Mild Pyelectesis (Hydronephrosis)

10) Nuchal Fold Thickness(not to be confused with N T at 11-13,6 weeks translucency).
• Nuchal edema in the second trimester between 15 and 23 weeks is known as the nuchal fold