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': 'Karyotyping of fetus can be done through all of the following invasive methods except \nSelect and explain. \nA. Amniocentesis, B. Cordocentesis, C. Chorionic villous sampling, D. Fetal skin biopsy', 'role': 'user'}, {'content': "Answer: D \nExplanation: fetal skin injuries due to amniocentesis might be rapid and complete.\nWe would like to describe the procedures of fetal skin biopsy which may serve as a tool for prenatal detection of congenital defects.\nThe pregnant woman lies supine. Guided by palpation and fixation of the fetus with assistant's hands, the Vim-Silverman biopsy needle with the obturator is introduced through the abdominal and uterine walls on the median line between symphysis and navel. \nWhen the needle is advanced slightly into the fetal tissue, the obturator is replaced with the inner split needle. \nSeveral pieces of fetal skin (about 1 mmX2 mm in size) are obtained by repeated splitting with the inner needle.\nSo far this procedure has been tried for eight women who were in the second or third trimester of pregnancy", 'role': 'assistant'}]