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': 'In what period, following delivery, does the cardiac output return to the pre-pregnancy state? \nSelect and explain. \nA. 4 hours, B. 4 weeks, C. 6 weeks, D. 8 weeks', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Cardiac output returns to pre labour values by one hour following delivery and pre pregnancy level by 4 weeks. Cardiac output: It stas to increase from 5th week of pregnancy reaches a peak 40-50% at about 30-34 weeks. It increases fuher during labour (50%) and immediately following delivery (70%) over pre labour values. Increase in cardiac output is due to: Increased blood volume To meet the additional oxygen required due to increased metabolic activity during pregnancy. Ref: Textbook of Obstetrics By D.C Dutta, 6th edn, page 53', 'role': 'assistant'}]