Soft markers e.g. nuchal fold thickness are minor ultrasound findings during pregnancy. These are not structural anomalies but can indicate an increased risk of certain conditions, such as chromosomal defects like fetal aneuploidy, or non-chromosomal abnormalities such as cardiac structural defects. These markers are typically identified during the second-trimester anomaly scan.
These markers often require correlation with other risk factors, such as maternal age and serological results, to determine their significance
Here are some common antenatal soft markers:
- Increased nuchal fold thickness: >6 mm
- Fetal Ventriculomegaly: >10 mm
- Hypoplastic/absent nasal bone
- Echogenic intracardiac focus (EIF)
- Choroid plexus cyst
- Echogenic bowel
- Shortened fetal long bones: less than 3rd centile for gestational age
- Short femur
- Short humerus
- Fetal pyelectasis
- Renal pelvic dilation greater than 4-5 mm.
- Single umbilical artery.
- Enlarged cisterna magna.
- Clenched fists.
Soft markers were originally introduced to prenatal ultrasonography to improve the detection rate (DR) of trisomy 21. Soft markers are identified in the mid-trimester of pregnancy. They most commonly do not represent a structural abnormality and may be normal variants. But are noteworthy because of their association with an increased aneuploidy risk.
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