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Pregnancy and the Heart

Circulatory System Changes

When you become  pregnant, your heart has to work harder than ever. As a result, you may notice certain symptoms such as swollen "ankles, fatigue, mild shortness of breath, and frequent urination. "These are typical symptoms, and usually are nothing to worry about," says Dr. Loryn Feinberg, cardiologist at Beth Israel Deaconess Medical Center.

These symptoms result from changes in your circulatory system due to your pregnancy. Cardiac output, for instance, is dramatically increased. This means that the amount of blood that your heart pumps out each minute goes up -- by about 30 to 40 percent.

Heart Rate and Blood Volume Increases

Your heart rate and blood volume also increase, while your blood pressure is likely to decline slightly. Your heart rate may increase by 10 to 15 beats per minute, or more. Blood volume goes up by 40 to 50 percent during the first trimester and remains high throughout your pregnancy. And your blood pressure may drop due to hormonal changes, the addition of the placenta to your own circulation, and because more blood is directed to your uterus. These are all normal changes of pregnancy, and are designed to ensure that your baby has a sufficient supply of blood, oxygen and other nutrients, Feinberg says.

Changes Start at Six Weeks

The demands on your circulatory system typically begin and rise from around six weeks of gestation. They then remain stable starting at around the beginning of the third trimester and increase again at the onset of labor and delivery. Most of the cardiac and vascular changes of pregnancy return to normal by eight weeks, but sometimes take up to twelve weeks to fully normalize.

Cardiac Complications

Few Pregnancies Affected

While these changes are considered normal, there is a small chance that cardiac changes may complicate your pregnancy. "About two percent of pregnancies in the United States are complicated by maternal heart disease,"says Feinberg.

Existing Heart Disease

"The cardiovascular demands of pregnancy can bring out symptoms in women with existing  heart disease who were previously asymptomatic, and a woman should be aware of any unusual symptoms that seem out of proportion to the typical symptoms of pregnancy, and alert her physician if they are present," she says.

Symptoms to Watch Out For

Such symptoms would include:

  • Progressive shortness of breath
  • Chest discomfort
  • Fainting
  • Severe lightheadedness
  • New onset of palpitations -- the sensation that the heart is racing or beating irregularly

Diagnosing Problems

An  echocardiogram can diagnose and evaluate any suspected cardiac disease in a pregnant woman. "This test uses ultrasound to visualize the chambers and valves of the heart, and enables cardiologists to detect any thickening or weakening of the heart muscle, valvular leaking, or enlargement of the chambers of the heart," Feinberg says. "It can also detect fluid surrounding the heart, which can be seen in a small amount in about 25 percent of pregnant women. Because there is no radiation involved, it is safe in pregnancy as well."

Evaluation Is Important

Risk Factors

Women with pre-existing cardiovascular risk factors, of course, are at higher risk for complications. These may include diabetes, high cholesterol, obesity,  hypertension and smoking. These conditions may have an important impact on the mother and the baby.

Pre-existing Conditions

"Women of childbearing age may have a pre-existing cardiovascular condition," Feinberg says. These women may do well during pregnancy, but ideally should be evaluated by a cardiologist prior to becoming pregnant, and should be followed throughout pregnancy by a cardiologist as well.

Such conditions may include:

Lower Your Risks

"This enables you and the physician to discuss your potential risk of complications during pregnancy, including potential risks to your baby, determine how to lower those risks, and how to achieve a successful pregnancy, including labor and delivery," she says.

Contact Information

Women's Cardiovascular Health Program
CardioVascular Institute
Beth Israel Deaconess Medical Center
330 Brookline Avenue
Boston, MA 02215