This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Prenatal Diagnosis, Subject name: Gynaecology & Obstetrics
[{'content': 'Fetal nuchal skin thickness is useful in detecting: \nSelect and explain. \nA. Fetal infection, B. Down syndrome, C. Anencephaly, D. Hydrops fetalis', 'role': 'user'}, {'content': "Answer: B \nExplanation: Nuchal thickness should be less than 3 mm in 12 to 13 weeks It should be < 6 mm after 14 weeks and it is called as nuchal fold Nuchal thickness/fold > 6 mm after 14 weeks is suggestive of down's syndrome", 'role': 'assistant'}]