<prompt> In what period, following delivery, does the cardiac output return to the pre-pregnancy state?4 hours4 weeks6 weeks8 weeks  <response>: 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 