This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diagnosis in Obstetrics, Subject name: Gynaecology & Obstetrics
[{'content': "Chorionic villous sampling is done in all except: \nSelect and explain. \nA. Phenylketonuria, B. Down's syndrome, C. Neural tube defect, D. Thalassemia/sickle cell anemia", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. is c, i.e. Neural tube defectChorionic villi sampling cannot detect structural abnormalities like neural tube defect."The indications of CVS and amniocentesis are usually the same, however disorders that specifically require analysis of amniotic fluid liquor such as neural tube defects are not amenable to prenatal diagnosis by CVS"Ref. Obs. and Gynae Beckman 5/e, p 45', 'role': 'assistant'}]