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': 'Investigation of choice for diagnosing downs syndrome at 15 weeks of gestation in a mother with a history of delivering a down syndrome baby is which of the following: \nSelect and explain. \nA. Triple screen test, B. Amniocentesis, C. Chorionic villous biopsy, D. Ultrasonography', 'role': 'user'}, {'content': "Answer: B \nExplanation: Amniocentesis is the investigation of choice for the diagnosis of downs syndrome. It is done between 14-16 weeks of gestation. It is performed in the context of prior history of a child with downs syndrome, advanced maternal age, abnormal triple or quad assay. Ref: Harrison's Principles of Internal Medicine, 17th Edition, Page 409 ; Textbook of Obstetrics By D.C.Dutta, 6th Edition, Page 107", 'role': 'assistant'}]