Pregnancy causes wide-ranging and profound changes in the expectant mother’s cardiovascular and circulatory system. For example, during the later stages of pregnancy, cardiac output increases between 30 and 50 percent. During labor, the mother’s cardiac output increases up to 80 percent. This increase is connected to the greater volume of blood circulating in the mother’s body and her increased heart rate, which is typically increased by 15 to 20 beats per minute. Despite the increased blood volume and cardiac output, however, blood pressure typically falls during a healthy pregnancy.

In women with existing heart disease, pregnancy carries extra risks. Their heart disease may become worse, or they may have to stop taking medications to control their disease. For example, statin medications, which are used to lower cholesterol, and ACE inhibitors, which are used to treat heart failure and hypertension, are not recommended during pregnancy. In years past, rheumatic heart disease was the most common cardiac complication among pregnant women. However, because of improved medical techniques that enable more infants to survive to childbearing age, congenital heart disease is now the leading cardiac complication among pregnant women. Also, because more women are postponing childbirth until they are in their 30s or 40s, it is more common to see expectant mothers with high blood pressure, diabetes and elevated cholesterol levels.

Any cardiac condition is a cause for concern, and heart patients who wish to become pregnant, or who are pregnant, are strongly encouraged to consult with their physician. The standard check-up for pregnant heart patients includes a medical history, physical examination, echocardiogram and electrocardiogram. These tests provide the physician with a complete picture of how the expectant mother’s heart and circulatory system are responding to the pregnancy.

If there is concern, bed-rest may be ordered. Studies have shown that the stress placed upon the heart depends in part on the expectant mother’s posture. Lying down can decrease the cardiac output by up to 30 percent. Conversely, however, some heart disease patients are at increased risk for blood clots during their pregnancy. Blood clots are a leading cause of maternal death among all women, but women who have certain inherited conditions, or who have artificial heart valves, are at especially elevated risk. In this case, the physician may recommend standing or sitting in certain positions and staying active to encourage adequate blood flow through the legs, where blood clots normally form.

During delivery, many physicians will allow the expectant mother to go into labor naturally and attempt a vaginal delivery. Studies have shown that vaginal deliveries pose less risk to heart patients than Caesarean deliveries. If, however, the mother is at an elevated risk level, then the physician may recommend inducing labor under controlled circumstances. Overall, a pregnant woman’s risk level from heart disease depends on the nature of the disease. Maternal cardiac conditions that carry the lowest overall risk to the mother and fetus include:

Cardiac conditions that carry moderate risk to the mother and fetus include:

• Narrowing of the aortic valve (aortic stenosis), which may require surgical repair before pregnancy is recommended
  
  
• Narrowing of the mitral valve (mitral stenosis)
  
  
• History of heart attack
  
  
• Marfan syndrome (with a normal aorta)
  
  
• Tetralogy of Fallot (a type of heart defect)
  
  
• Coronary artery disease, which is relatively rare among childbearing women but may result in heart attack
  
  
• Various arrhythmias, which may range from harmless to very dangerous

High-risk conditions include:

• Eisenmenger syndrome (50 percent of these women do not survive pregnancy)
  
  
• Severe forms of cardiomyopathy, especially affecting the left ventricle
  
  
• Peripartum cardiomyopathy (a gestational heart-related condition)
  
  
• Pulmonary hypertension (high blood pressure in the vessels of the lungs)
  
  
• Artificial heart valves that require anticoagulation
  
  
• Heart failure