Which of the following is an ultrasound finding for Trisomy 21?

The presence of an absent nasal bone is a significant ultrasound finding that is associated with Trisomy 21, also known as Down syndrome. In fetuses with this condition, the nasal bone is often smaller or not visible during the mid-trimester ultrasound, particularly around 11 to 14 weeks of gestation. This finding can suggest increased risk for chromosomal abnormalities, including Trisomy 21, when combined with other soft markers or maternal serum screening results.

The absence of the nasal bone contributes to the assessment of the fetal risk profile for Down syndrome. It is particularly relevant in conjunction with other markers such as nuchal translucency measurements. When evaluating these findings collectively, healthcare providers can better counsel expectant parents on potential risks and the need for further diagnostic testing.

Other findings, while associated with different conditions or configurations, do not specifically indicate Trisomy 21. For instance, endocardial cushion defects can be associated with several congenital heart diseases, not exclusively with Trisomy 21, and while macrocpehaly and cystic hygroma can be present in numerous conditions, including some syndromes, they are not specific indicators of Trisomy 21. Therefore, the absence of the nasal bone remains a highly