Normal cardiovascular adaptation to pregnancy
Normal pregnancy is characterized by profound hemodynamic changes. These begin early in pregnancy and include a fall in vascular resistance which induces an increase in blood volume and stroke volume. Heart rate and cardiac output also rise. Arterial blood pressure is reduced. The adaptation is most prominent in the first half of pregnancy. To cope with these hemodynamic challenges, the left ventricle hypertrophies, thereby preserving systolic and diastolic function. Peripheral arterial resistance is decreased and compliance and distensibility are increased. Venous capacitance is greatly enhanced. Uteroplacental blood flow augments with gestation to meet the increased needs of a growing fetus. Maternal cerebral blood flow is reduced. The influence of these major macrovascular changes on microvascular perfusion remains to be elucidated. During labor and delivery, cardiac output further rises. Postpartum, most hemodynamic parameters are rapidly reversed within weeks. Structural changes normalize within several months.