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: Chorionic villi are extremely good source of fetal DNA and thus ideal for PCR and DNA analysis to diagnose single gene defects like hemoglobinopathies,cysticfibrosis,duchenne muscular dystrophy.Represents confined placental mosaicism.It can be used to diagnose storage diseases like Tay Sachs and Gaucher&;s disease. TEXTBOOK OF OBSTETRICS,SHEILA BALAKRISHNAN,Pg no:503,2nd edition', 'role': 'assistant'}]