gynecology and obstetrics
Heart Disease in Pregnancy
Pathophysiology of Heart Disease in Pregnancy
Pregnancy stresses the cardiovascular system, often worsening known heart disease; mild heart disease may first become evident during pregnancy. Stressors include decreased hemoglobin and increased blood volume, stroke volume, and eventually heart rate. Cardiac output increases by 30 to 50%. These changes become maximal between 28 and 34 weeks gestation. During labor, cardiac output increases about 20% with each uterine contraction; other stressors include straining during the 2nd stage of labor and the increase in venous blood returning to the heart from the contracting uterus. Cardiovascular stressors do not return to prepregnancy levels until several weeks after delivery. 