How reliable are soft markers ??

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

Trisomy 21 (Down syndrome) 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 triploidy.

Characteristics of Soft Markers are: Such 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 of presence /Absence of them.

Prenatal ultrasonography during the second trimester (15-22wks) provides a “genetic sonogram” that is used to identify morphologic features of fetal Down syndrome.

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)

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1) 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
• The measurement of NT has to be taken 
-- In the transcerebeller plane which includes the cerebellum, occipital bone, and cavum septum pellucidum 
-- placement of calipers from the outer edge of occipital bone to the outer edge of the skin
Cut-off For Trisomy 21 : 6 mm : DR- 33 % ;
FPR - 0.1%
More recent studies suggest that gestational age-specific criteria should be used, because nuchal thickness normally increases with gestational age.

What to do on NT >6mm?

1) Detailed Ultrasound examination of fetus for other markers/anomaly
2) To Calculate the risk of aneuploidy after considering single or multiple markers based on the Study of Nicolaides et al .
3) Counsel the patient & relatives with the final Risk of Trisomies..
4) Act as per patient’s wish….

Here I have discussed about one of the 9 markers, I will post about rest of the markers soon....

Chromosomal abnormalities occur in 0.1% to 0.2% of live births. Of which Trisomy 21 (Down syndrome) is the most common karyotypic abnormality in live-born infants (1 per 800 live births) and is a leading cause of mental retardation. Sonographic findings in fetuses with Down syndrome include both structural abnormalities and non-structural abnormalities or “markers. Other Sonographically detectable aneuploidies include trisomy 13, trisomy 18, monosomy X, and triploidy.

Various methods have been used to identify women at risk of carrying a fetus with trisomy 21, including consideration of maternal age, biochemical markers amniocentesis is and prenatal ultrasound. Amniocentesis can reliably determine fetal karyotype, but there is a 0.5% to 1.0% fetal mortality rate associated with this procedure.

Few learning points on anomaly scan:-A second-trimester ultrasound scan is usually done at 18 to 22 weeks. Two types of sonographic markers suggestive of aneuploidy can be observed in the second trimester. Major fetal structural abnormalities comprise the first type. There are many other, less-defined features that have been given less significance as “possible markers” of aneuploidy, and these are collectively called “soft markers” of aneuploidy. Although not pathologic themselves, these markers have been used to screen for, or adjust the risk for, Down syndrome and other aneuploidies.

Soft markers may be seen in the normal fetus but such prevalence is more often have an increased incidence in infants with chromosomal abnormalities. These markers are nonspecific, often transient, and can be readily detected during the second-trimester ultrasound. Thus, prenatal ultrasonography during the second trimester provides a “genetic sonogram” that is used to identify morphologic features of fetal Down syndrome.

Major and Soft Markers of Aneuploidy

For a number of years, members of the ultrasound community involved in obstetric sonography have been grappling with a controversial issue centered on soft markers of aneuploidy. Major abnormalities are observed in fewer than 25% of affected fetuses in most studies whereas 1 or more soft markers may be observed in at least 50% of cases. Prenatal ultrasound attempts to detect the soft markers; ultrasound in the second trimester currently diagnoses 50% to 70% of cases of Down syndrome, 70% to 100% trisomy 18, and 90% to 100% trisomy 13.

The most commonly studied soft markers of aneuploidy include a thickened nuchal fold, rhizomelic limb shortening, mild fetal pyelectasis, echogenic bowel, and echogenic intracardiac focus (EIF) and choroid plexus cyst (CPC). There is a great deal of interest in the ultrasound detection of aneuploidy, as evidenced by the large number of publications in the literature on this topic. Unfortunately, studies evaluating the significance of the soft markers of aneuploidy vary widely and show contradictory results. We review the most common ultrasonographic soft markers used to screen aneuploidy and discuss ultrasonographic technique and measurement criteria for the detection of soft markers. We also review the clinical relevance of soft markers to aneuploidy risk assessment and evidence-based strategies for the management of affected pregnancies with each of these markers in light of current literature.

. Ultrasonographic soft markers of aneuploidy in second trimester: are we lost?

Chromosomal abnormalities occur in 0.1% to 0.2% of live births, and the most common clinically significant aneuploidy among live-born infants is Down syndrome (trisomy 21). Other sonographically detectable aneuploidies include trisomy 13, 18, monosomy X, and triploidy. Second-trimester ultrasound scan detects 2 types of sonographic markers suggestive of aneuploidy. Markers for major fetal structural abnormalities comprise the first type; the second type of markers is known as "soft markers" of aneuploidy. These latter markers are nonspecific, often transient, and can be readily detected during the second-trimester ultrasound. The most commonly studied soft markers of aneuploidy include a thickened nuchal fold, rhizomelic limb shortening, mild fetal pyelectasis, echogenic bowel, and echogenic intracardiac focus and choroid plexus cyst. There is a great deal of interest in the ultrasound detection of aneuploidy, as evidenced by the large number of publications in the literature on this topic. Unfortunately, studies evaluating the significance of the soft markers of aneuploidy vary widely and show contradictory results. In this article, we review the most common ultrasonographic soft markers used to screen aneuploidy and discuss ultrasonographic technique and measurement criteria for the detection of soft markers. We also review the clinical relevance of soft markers to aneuploidy risk assessment and evidence-based strategies for the management of affected pregnancies with each of these markers in light of current literature. Obstet Gynecol Sci. 2015 Nov;58(6):446-52. doi: 10.5468/ogs.2015.58.6.446. Epub 2015 Nov 16.