Antenatal soft markers on ultrasound
Antenatal soft ultrasound markers are fetal sonographic findings that are generally not abnormalities as such but are indicative of an increased age adjusted risk of an underlying fetal aneuploidic or some non chromosomal abnormalities.
Most of the described features do not constitute a structural defect and may be detected on antenatal screening, typically during a second trimester (anatomy) scan. Many are transient.
What's included or not appears to depend on the respective authorities in each region, and remains dynamic, with certain markers periodically emerging, or conversely losing favor.
The following are markers in common use at the time of writing. The list includes features having an association with:
An increased risk of aneuploidy and in some cases non-chromosomal problems
- increased nuchal thickness: >6 mm
- fetal ventriculomegaly: >10 mm
- hypoplastic/absent nasal bone
- echogenic intracardiac focus (EIF)
- choroid plexus cysts
- echogenic bowel
- shortened fetal long bones: less than 3 centile for gestational age
- aberrant right subclavian artery
An increased risk of non-chromosomal abnormalities when seen in isolation
- fetal pyelectasis/fetal renal pelvic dilatation: antero-posterior diameter of the renal pelvis >4-5 mm
- single umbilical artery (SUA)
- enlarged cisterna magna
Soft markers of undefined association
Correct interpretation of these often requires correlation with other risk factors such as history, maternal age and maternal serological results.