This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Gynaecology & Obstetrics
[{'content': 'Establishment of fetoplacental circulation seen at- \nSelect and explain. \nA. 11 to 13 days, B. 20 to 22 days, C. 7 days, D. 25 to 26 days', 'role': 'user'}, {'content': "Answer: B \nExplanation: Impoant Events Following Feilization 0' hour Feilization (day-15 from LMP) 30 hours 2 cell stage (blastomeres) 40-50 hours 4 cell stage 72 hours 12 cell stage 96 hours 16 cell stage. Morula enters the uterine cavity 5th day Blastocyst 4-5th day Zona pellucida disappears 5-6th day Blastocyst attachment to endometrial surface 6-7th day Differentiation of cyto and syncytiotrophoblast layers 10th day Synthesis of hCG by syncytiotrophoblast 9-10th day Lacunar network forms 10-11th day * Trophoblasts invade endometrial sinusoids establishing uteroplacental circulation * Interstitial implantation completed with entire decidual coverage REF : DUTTA BOOK OF OBESTETRICS", 'role': 'assistant'}]