This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ULTRASOUND, Subject name: Radiology
[{'content': 'Which of the following ultrasound marker is associated with greatest increased risk for Trisomy 21 in fetus: \nSelect and explain. \nA. Echogenic foci in hea, B. Hyperechogenic bowel, C. Choroid plexus cysts, D. Nuchal skin fold', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Increased nuchal skin fold confers the highest risk of aneuploidy and is the most powerful second trimester ultrasound marker, > 99% specificity for Down Syndrome. The probability of Down Syndrome is increased when multiple soft markers are present.', 'role': 'assistant'}]