Which of the following is the most predictive second trimester marker for Down syndrome available from ultrasound?

The thickened nuchal fold is indeed recognized as one of the most predictive second trimester markers for Down syndrome seen on ultrasound. Measurement of the nuchal fold is typically performed during the second trimester (11-14 weeks) and is evaluated as part of the detailed anatomy scan. A nuchal fold measurement greater than 6 mm is associated with an increased risk of chromosomal abnormalities, including Down syndrome (trisomy 21).

In terms of sensitivity and specificity, the thickened nuchal fold has been consistently studied and shown to have a stronger correlation with Down syndrome compared to other markers evaluated during the second trimester. This makes it a crucial component in screening for aneuploidies, helping practitioners identify pregnancies at higher risk for these conditions.

While other markers, like the echogenic intracardiac focus, pyelectasis, and sandal gap, can also be seen in pregnancies affected by Down syndrome, they are less predictive individually. The echogenic intracardiac focus and pyelectasis can be seen in normal pregnancies and are considered soft markers. The sandal gap, which refers to a wider gap between the first and second toes, can also be present in normal variations. Therefore, the thickened nuchal fold