This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular System, Subject name: Gynaecology & Obstetrics
When does the cardiac output returns to pre pregnancy state? 
Select and explain. 
A. 4 hours, B. 4 weeks, C. 6 week, D. 8 week
B: 4 weeks
Answer: B: 4 weeks 
Explanation: ANSWER: (B) 4 weeksREF: Dutta's obs 6th edp. 53Cardiac output in pregnancy:Starts to increase from 5th week of pregnancy, reaches its peak to 40-50% of baseline at about 30-34* weekCO is highest in right or left lateral or knee chest position and lowest in supine or sitting positionCardiac output is higest post delivery.Return to pre labour values by 1 hour and pre-pregnant levels by 4th week.