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