This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
[{'content': 'Fetal nuchal skin thickness is useful in detecting: March 2012 \nSelect and explain. \nA. Fetal infection, B. Down syndrome, C. Anencephaly, D. Hydrops fetalis', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans: B i.e. Down syndrome Increased fetal nuchal skin thickness (in first trimester) of more than 3 mm by TVS is a strong marker for chromosomal anomalies (trisomy 21, 18, 13, triploidy and Turner's syndrome).", 'role': 'assistant'}]