This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
[{'content': 'Chorionic villus sampling is generally performed between \nSelect and explain. \nA. 8 to 10 weeks, B. 10 to 13 weeks, C. 15 to 18 weeks, D. 20 to 24weeks', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Biopsy of chorionic villi is generally performed between 10 and 13 weeks gestation. Although most procedures are performed to assess fetal karyotype, numerous specialized genetic tests can also be performed by chorionic villus sampling (CVS). The primary advantage of villus biopsy is that results are available earlier in pregnancy, allowing safer pregnancy termination if desired.', 'role': 'assistant'}]