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': 'The best time to do chorionic villous sampling is \nSelect and explain. \nA. Between 6-8 weeks, B. Between 7-9 weeks, C. Between 9-11 weeks, D. Between 11-13 weeks', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. is d i.e. Between 11 - 13 weeks Chorionic villi sampling "CVS is the second most common procedure for genetic prenatal diagnosis. Because this procedure is routinely performed at about 10 to 12 weeks of gestation, it allows for an earlier detection of abnormalities and a safer pregnancy termination, if desired."', 'role': 'assistant'}]