Ans. d. Immediately after delivery The highest volume overload in a paurient due to maximum cardiac output is seen immediately after delivery. "Peripheral vasodilation leading to a decrease in systemic vascular resistance is thought to be the first cardiovascular change associated with pregnancy (induced by progesterone). Cardiac output increases in response to this, by 20% at 8 weeks gestation and by up to 40-50% at 20-28 weeks gestation. Labour leads to fuher increases in cardiac output by 15% in the first stage and 50% in the second stage due to the combination of auto-transfusion of 300-500 ml of blood back into the circulation with each uterine contraction, and sympathetic stimulation caused by pain and anxiety. Cardiac output increases again immediately after delivery due to auto-transfusion of blood uterine contraction and relief of aoocaval compression. This may increase cardiac output by as much as 60-80%, followed by a rapid decline to pre-labour values within 1 houry Physiological Changes in the Cardiovascular System During Pregnancy Peripheral vasodilation leading to a decrease in systemic vascular resistance is thought to be the first cardiovascular change associated with pregnancy (induced by progesterone). Cardiac output increases in response to this, by 20% at 8 weeks gestation and by up to 40-50% at 20-28 weeks gestation. This is achieved predominantly an increase in stroke volume (due to an increase in ventricular end-diastolic volume, wall muscle mass, and contractility) but also by an increase in hea rate Labour leads to fuher increases in cardiac output by 15% in the first stage and 50% in the second stage due to the combination of auto-transfusion of 300-500 ml of blood back into the circulation with each uterine contraction, and sympathetic stimulation caused by pain and anxiety Cardiac output increases again immediately after delivery due to auto-transfusion of blood uterine contraction and relief of aoocaval compression. This may increase cardiac output by as