Heart Disease and Pregnancy

Heart disease in the mother complicates about 1% of all pregnancies. Congenital heart lesions make up about half of all cases of heart disease in pregnant mothers. Although the management of this condition has improved over the years and there are new surgical techniques, heart disease remains a major cause of maternal death throughout the world.

Pregnancy has a profound effect in women who have underlying heart disease. During pregnancy, the volume of blood in the mother’s body increases dramatically to meet the needs of the growing baby. As a result, the heart has to work that much harder to pump blood through the mother’s body.

Much of the increase in the output of the heart occurs during early pregnancy. As a result, a pregnant woman with heart disease may have additional cardiovascular problems by the middle of her pregnancy. The outcome for a pregnant mother with heart disease depends on the capacity of her heart, whether there are other complications during pregnancy, and what type of medical care she receives. For some women, bed rest may be required throughout pregnancy.

Types of heart disease

Before discussing the different types of heart disease, it is helpful to try to understand a bit about the structure of the cardiovascular system. The cardiovascular system consists of the heart and blood vessels called veins and arteries. The heart pumps blood throughout the body. It contains two upper chambers called atria and two lower chambers called ventricles. Veins bring blood to the vena cava and then to the heart. The aorta brings blood away from the heart to the arteries, where the blood is distributed to other areas of the body.

There are many different types of heart disease, and they can be categorized into three groups according to the risk of death that they pose to the mother in pregnancy.

Group 1: Heart disease with 1% or lower risk to the mother in pregnancy

  • atrial septal defects: a hole between the two upper, or receiving, chambers of the heart, called the atria
  • ventricular septal defects: a hole between the two lower, or pumping, chambers of the heart, called the ventricles
  • patent ductus arteriosus: a condition where an important fetal structure in the heart did not close properly after birth
  • tricuspid disease: a narrowing of the flaps between the right atrium and right ventricle of the heart
  • tetralogy of Fallot, corrected: a condition where there is a hole between the ventricles of the heart, there are obstructions between the right ventricle and the lungs, the aorta lies right over the hole between the ventricles, and the right ventricle tissue becomes thickened; in this case, the condition has already been corrected with surgery
  • bioprosthetic valve: an artificial heart valve that has been implanted to replace a defective valve
  • mitral stenosis, New York Heart Association class I or II: a mild to moderate narrowing of the valve between the left atrium and left ventricle of the heart

Group 2: Heart disease with 5% to 15% risk to the mother in pregnancy

  • mitral stenosis, New York Heart Association class III or IV: a more serious narrowing of the valve between the left atrium and left ventricle of the heart
  • aortic stenosis: a narrowing of the valve leading from the left ventricle to the aorta
  • aortic coarctation without valve involvement: a narrowing of the aorta somewhere along its length
  • tetralogy of Fallot, uncorrected: tetralogy of Fallot which was not corrected before pregnancy
  • previous heart attack
  • Marfan syndrome, normal aorta: a connective tissue disorder that affects the heart, blood vessels, skeleton, lungs, and eyes

Group 3: Heart disease with 25% to 50% risk to the mother in pregnancy

  • pulmonary hypertension: high blood pressure in the arteries that move blood from the heart to the lungs
  • aortic coarctation with valve involvement
  • Marfan syndrome with valve involvement

Treatment of heart disease during pregnancy

Women with heart disease may need to be followed by a multidisciplinary team that specializes in heart disease in pregnancy. Some heart diseases need to be treated with specific drugs.

Women who have had a valve replacement usually require a drug called an anticoagulant, such as heparin, throughout pregnancy until just before delivery, and then the drug will need to be restarted shortly after delivery. Note that another anticoagulant, warfarin​, is thought to be a teratogen.

Women with mitral stenosis may need a drug called a beta-blocker to slow the heart rate response to activity and anxiety.

Women who have had a heart attack may need an array of drugs such as nitrates, calcium channel blockers, or beta-blockers.

Women with mild heart disease generally go through pregnancy without any major problems. To be on the safe side, special attention should be given toward preventing and recognizing the early signs of heart failure:

  • shortness of breath
  • persistent wheezing, sometimes with a cough
  • fatigue
  • difficulty carrying out normal activities
  • increased heart rate and palpitations

If you are pregnant and you have mild heart disease, you should make sure to avoid people who have respiratory infections, as these infections can lead to heart failure. Consider getting a flu shot and refrain from smoking.

If you have serious heart disease and are pregnant, you will need to carefully consider the risks and cooperate fully with your doctor’s plan of care for you. If you are early into your pregnancy, you may want to consider ending the pregnancy through therapeutic abortion. If you choose to continue the pregnancy, prolonged hospitalization and bed rest will usually be required.

Labour and delivery in women with heart disease

In general, women with mild heart disease should attempt childbirth vaginally unless there is another complication that requires a caesarean section. Despite the physical effort required for vaginal birth, the outcomes are better and the risks for the mother are lower when compared with caesarean section. Pain relief during childbirth is very important, and may involve medications called intravenous analgesics or epidurals. You will be closely monitored during labour and delivery.

Likewise, pregnant women with serious heart disease should still try to deliver vaginally, if their caregiver recommends a vaginal birth. Very ill women do not tolerate major surgical procedures such as caesarean section very well. If possible, the delivery should be done in a hospital that has extensive experience with complicated cardiac disease.

Effects of maternal heart disease on the unborn baby

Babies of mothers with heart disease may inherit congenital heart problems. Congenital heart disease in the unborn baby can sometimes be diagnosed during pregnancy using a procedure called a fetal echocardiogram. Sometimes congenital heart disease can be treated with surgery shortly after birth.

Nicolette Caccia, MEd, MD, FRCSC

Rory Windrim, MB, MSc, FRCSC