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Heart Disease and Pregnancy

How the heart works

The cardiovascular system, composed of the heart and blood vessels, is responsible for circulating blood throughout your body to supply the body with oxygen and nutrients.

The heart is the muscle that pumps blood filled with oxygen and nutrients through the blood vessels to the body tissues.

It is made up of four chambers (two atria and two ventricles) that receive blood from the body (the atria) and pump out blood to it (the ventricles); the right atrium receives blood from the body, which is high in oxygen and low in carbon dioxide; the right ventricle pumps the blood from the right atrium into the lungs to provide it with oxygen and remove carbon dioxide; the left atrium receives blood from the lungs, which is rich in oxygen; the left ventricle pumps the blood from the left atrium into the body, supplying all organs with blood; and blood vessels, which compose a network of arteries, and veins that carry blood throughout the body.

Arteries transport blood from the heart to the body tissues.

Veins carry blood back to the heart.

Four valves to prevent backward flow of blood.

Each valve is designed to allow the forward flow of blood and prevent the backward flow.

An electrical system of the heart stimulates contraction of the heart muscle.

The heart in pregnancy

The heart is the hardest working muscle in the human body. Located almost in the center of the chest, the adult human heart is about the size of one fist.

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

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

During labor and delivery, there can be great changes in the heart and vascular system. Large amounts of blood move from the uterus into the mother's circulation as the 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 the heart rate slows. Excessive blood loss with delivery can change the heart rate, blood pressure, and cardiac output.

Diagnosing heart disease in pregnancy

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

What are the symptoms of heart disease?

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

  • Difficulty breathing, especially at night or without exertion
  • Inability to perform normal activities
  • Light-headedness or fainting
  • Palpitations (irregular heartbeat)
  • Heart murmur or click
  • Enlarged heart (more than the normal enlargement with pregnancy)
  • 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 physician 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, diagnostic procedures for heart disease may include:

  • Electrocardiogram (ECG or EKG). A test that records the electrical activity of the heart, shows abnormal rhythms (arrhythmias or dysrhythmias), and detects heart muscle damage.
  • Echocardiography. A procedure that evaluates the structure and function of the heart by using sound waves recorded on an electronic sensor that produce a moving picture of the heart and heart valves.

Cardiac conditions and pregnancy

Normal physical changes in pregnancy may cause problems for women with cardiac disease. Prenatal care and close watch of women with heart disease are important in healthy outcomes for mother and baby. There is approximately an 8 to 10 percent risk that a mother with a congenital heart defect (CHD) will have a baby with some type of CHD, but not necessarily the same defect as the mother. High-risk prenatal monitoring of the mother and baby is recommended. Some common cardiac conditions that may be affected by pregnancy include the following:

  • Mitral stenosis. In this condition, the heart valve between the left atrium and left ventricle is narrowed or constricted. This may be due to a congenital malformation of the valve at birth or caused by scarring from an infection, such as rheumatic fever during childhood.

    The normal cardiovascular changes with pregnancy can cause problems for women with mitral stenosis, including difficulty breathing, irregular heartbeat, and lung congestion. Medication may be needed to regulate the heart. Some women may have disease serious enough to need repair or replacement of the valve during pregnancy. Because of the effects of labor and birth on the heart, intensive care may be required after delivery. Normal cardiovascular changes that occur after delivery may cause serious illness in the mother. Women with prosthetic heart valves may require antibiotics for complicated deliveries to prevent endocarditis. 
  • Atrial septal defect (ASD). In this condition, there is an abnormal opening between the two upper chambers of the heart—the right and left atria—causing an abnormal blood flow through the heart. This is the most common congenital (present at birth) heart defect in adults. Most women with a small ASD generally do not have serious complications with pregnancy, however, fatigue is common. Women with large unrepaired ASD and Eisenmenger Syndrome should avoid pregnancy.
  • Ventricular septal defect (VSD). In this condition, there is an abnormal opening between the two lower chambers of the heart—the right and left ventricle—causing an abnormal blood flow through the heart. Because the 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. Some women with large unrepaired VSD and Eisenmenger Syndrome should avoid pregnancy. 
  • Aortic stenosis (AS). In this condition, the aortic valve between the left ventricle and the aorta did not form properly and is narrowed, making it difficult for the heart to pump blood to the body. A normal valve has three leaflets or cusps, but a stenotic valve may have only one cusp (unicuspid) or two cusps (bicuspid). Women with severe aortic stenosis may be advised against becoming pregnant because of the effects of pregnancy on this heart condition. Evaluation of the aortic root and entire aorta is also important for women with aortic stenosis, to check for any enlargement that could worsen during pregnancy and affect decisions regarding mode of delivery (i.e., vaginal vs. cesarean section). Intensive care may be required for close monitoring during or after delivery. Women with prosthetic heart valves 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 the 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, occurring in about 12 percent. Most women have no difficulty in pregnancy with MVP.

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