This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Labour - normal, abnormal, malposition, malpresentation and their management, Subject name: Gynaecology & Obstetrics
[{'content': 'Average duration of 3rd stage of labor is: \nSelect and explain. \nA. 45 minutes, B. 15 minutes, C. 60 minutes, D. 5 minutes', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Stage Definition- First: From the onset of TRUE labor to full dilation of cervix. Average duration: 12 hours in primigravida and 6 hours in multigravida. Second: From full dilation of cervix to bih of the baby. Median duration is approximately 50 minutes in primigravida and 20 minutes in multigravida. Third: From bih of the baby to delivery of the placenta. Average duration: 15 minutes in both primigravida and multigravida. Fouh: 1-hour observation period, following delivery of the placenta.', 'role': 'assistant'}]