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Pregnancy and Preexisting Heart Disease

Your heart in pregnancy

Your heart is the hardest working muscle in your body. Located almost in the center of your chest, your heart is about the size of one fist.

Beating at an average rate of 80 times a minute, your heart beats about 115,000 times in one day, or 42 million times in a year. During an average lifetime, your heart will beat more than three billion times. It pumps an amount of blood that equals about one million barrels. Even at rest, your heart continuously works hard.

Beginning in your first trimester, your blood volume increases to approximately 50 percent more than before your pregnancy. The extra fluid puts an increased workload on your heart. Your heart responds by increasing its cardiac output. This is the amount of blood that goes through your circulatory system in one minute. Other body systems also respond. Blood pressure decreases to allow the increased blood volume to flow.

During labor and delivery, great changes in your heart and vascular system can occur. Large amounts of blood move from your uterus into your circulation, as your uterus contracts. This causes major changes in blood pressure, heart rate, and cardiac output. Epidural or spinal anesthesia may cause blood pressure to decrease.

After delivery, cardiac output increases and your heart rate slows. Excessive blood loss with delivery can change your heart rate, blood pressure, and cardiac output.

Diagnosing heart disease in pregnancy

Heart disease is a known possible complication of pregnancy. It occurs in about 1% of all pregnancies. Sometimes, heart disease is diagnosed before pregnancy. However, some women have unknown heart conditions that become apparent only during pregnancy.

What are the symptoms of heart disease?

The following are common symptoms of heart disease. However, every woman may experience them differently. Symptoms may include:

  • Difficulty breathing, especially at night or without exertion

  • Inability to perform normal activities, due to weakness or fatigue

  • Light-headedness or fainting

  • Palpitations (irregular heartbeat)

  • Cyanosis (blue-coloring due to low levels of oxygen in the blood)

The symptoms of heart disease may resemble other conditions or medical problems. Always consult your health care provider for a diagnosis.

How is heart disease diagnosed?

Diagnosis can be difficult because some of the normal symptoms of pregnancy are similar to the symptoms of heart disease. In addition to a complete medical history and physical examination, the following procedures can help diagnose your heart disease. 

  • Electrocardiogram (ECG or EKG). Records the electrical activity of your heart, shows abnormal rhythms (arrhythmias or dysrhythmias), and detects heart muscle damage.

  • Echocardiography. Evaluates the structure and function of your heart by using sound waves recorded on an electronic sensor. These produce a moving picture of your heart and heart valves.

Cardiac conditions and pregnancy

Normal physical changes in pregnancy may cause problems, if you have cardiac disease. You will need prenatal care, and to be closely watched to help ensure a healthy outcome for you and your baby. If you have a congenital heart defect (CHD), meaning a defect you've had since birth, there is a risk that your baby also will have a defect. It won't necessarily be the same type as yours. You will most likely need high-risk prenatal monitoring. Common cardiac conditions that may be affected by pregnancy include the following:

  • Mitral stenosis. The heart valve between your left atrium and left ventricle is narrowed or constricted. This may be due to a congenital malformation of your valve, or scarring from a childhood infection, such as rheumatic fever. Normal cardiovascular changes with pregnancy can cause problems if you have mitral stenosis. These include difficulty breathing, irregular heartbeat, and lung congestion. You may need medication to regulate your heart. You may have disease serious enough to need repair or valve replacement during pregnancy. Because of the effects of labor and birth on your heart, you may require intensive care after delivery. Normal cardiovascular changes that occur after delivery may cause serious illness. If you have prosthetic heart valves and you have a complicated delivery, you may require antibiotics to prevent endocarditis.

  • Atrial septal defect (ASD). An abnormal opening exists between the two upper chambers of your heart—the right and left atria—causing an abnormal blood flow through your heart. This is the most common congenital heart defect in adults. If you have a small ASD, you generally do not have serious complications with pregnancy, however, fatigue is common. If you have large unrepaired ASD, you should avoid pregnancy.

  • Ventricular septal defect (VSD). An abnormal opening exists between the two lower chambers of your heart—the right and left ventricle. This causes an abnormal blood flow through your heart. Because your heart becomes overworked, it may enlarge. Most women with small VSD do not have serious complications with pregnancy. Some may experience fatigue and palpitations as the pregnancy progresses. If you have large, unrepaired VSD, you should avoid pregnancy.

  • Aortic stenosis (AS). The aortic valve between the left ventricle and the aorta did not form properly and is narrowed. This makes it difficult for your heart to pump blood to your body. A normal valve has three leaflets or cusps, but a stenotic valve may have only one cusp (unicuspid) or two cusps (bicuspid). If you have severe aortic stenosis, your health care provider may advise you against becoming pregnant. This is because of the effects of pregnancy on this heart condition. If you have AS, it is important that you get an evaluation of your aortic root and entire aorta. This checks for any enlargement that could worsen during pregnancy. Your condition also affects decisions regarding mode of delivery (vaginal vs. cesarean section). You may need intensive care during or after delivery, so that you can be closely monitored. If you have prosthetic heart valves, you may require antibiotics for complicated deliveries to prevent endocarditis.

  • Mitral valve prolapse (MVP). Also known as click-murmur syndrome, Barlow's syndrome, balloon mitral valve, or floppy valve syndrome, this condition is characterized by a bulging of one or both of the mitral valve flaps during the contraction of your heart. One or both of the flaps may not close properly, allowing the blood to leak backward. This may result in a mitral regurgitation murmur. Most people have no symptoms of mitral valve prolapse.
    MVP is the most common congenital heart defect in women of childbearing age. Most women have no difficulty in pregnancy with MVP.