American Medical Association Family Medical Guide - American Medical Association [169]
How Heart Defects Develop
The heart of a fetus starts to develop early in pregnancy and is fully developed by the third month of pregnancy. Any disturbance in development during this critical period (such as a rubella infection; see page 508) can cause a heart defect. The cause of the vast majority of congenital heart abnormalities is unknown. In most cases, both genes and environmental factors are thought to interact to produce the defect, but specific environmental factors usually cannot be identified.
Although most congenital heart defects occur in otherwise healthy infants, they also can be present in children with broader genetic disorders such as Down syndrome (see page 955), Marfan syndrome (see page 967), or Turner syndrome (see page 957). An ultrasound (see page 510) of the fetus is often part of a prenatal examination during the first few months of pregnancy and provides a picture of the internal organs, including the heart. The doctor studies the fetus’s heart on the ultrasound and, if he or she suspects an abnormality, will recommend a more specialized test called a fetal cardiac ultrasound to get a more detailed image of the anatomy of the fetus’s heart.
Birth Defects
Abnormalities that are present in a child at birth are called birth defects or congenital abnormalities. Although they are present at birth, their effects may not become apparent until later in life. Birth defects can result from genetic or environmental factors or both. For many, the cause is unknown.
For most birth defects, the earlier a child is treated, the better the outcome for his or her development and physical and emotional health. In addition to medical treatment, a child who has a birth defect can often benefit from counseling by a mental health professional who can help him or her deal with the challenges presented by his or her abnormality. If your child has a birth defect, you might also benefit from counseling; ask your doctor to recommend a counselor or support group that can put you in touch with other parents who have a child with a similar birth defect.
Symptoms of Congenital Heart Defects
Many cases of congenital heart defects produce no symptoms, and the defect is detected during a routine examination of the heart. In some cases, symptoms are obvious. Sometimes symptoms are present at birth, and sometimes they don’t develop until childhood or much later. Some congenital heart defects that don’t produce symptoms early in life require surgery to prevent problems from developing later.
Lack of oxygen in the blood can cause blueness of the skin (cyanosis). Cyanosis is a common sign of congenital heart problems that allow blood lacking oxygen (deoxygenated blood) to circulate through the body. A baby with mild heart failure may have difficulty feeding (because he or she does not have enough energy to suck) and he or she may lose weight and cry less than usual. In severe heart failure, symptoms are more obvious—the child’s breathing is rapid and difficult even while resting, and his or her skin may be blue because of the lack of oxygen.
Diagnosing Congenital Heart Defects
A doctor can usually diagnose a congenital heart defect by examining the heart with a stethoscope, which enables him or her to hear the sounds made by the heart when the pumping chambers of the heart (ventricles) contract and the valves open and close. Sounds of blood flow that occur between the sounds of the valves are called murmurs, which can be normal or the sign of a heart abnormality. A harmless murmur is a common, normal sound of blood flow that can be heard in children after 2 to 3 years of age. These normal murmurs (also called innocent murmurs or functional murmurs) do not require any treatment.
If the child’s doctor has detected a murmur that suggests an abnormality, he or she will refer the child to a pediatric cardiologist (a doctor who specializes