Congenital heart disease (CHD) describes structural problems with the heart that are present at birth, affecting its walls, valves, or large blood vessels. The impacts of these issues range from mild, with no significant symptoms, to severe conditions requiring immediate medical intervention. As the most common type of birth defect, CHD affects nearly 1% of all live births in the United States annually. A CHD can alter the normal flow of blood through the heart, which affects how oxygen is delivered to the body. While some minor defects resolve on their own, about one in four babies with a CHD have a critical form requiring surgery within their first year.
Genetic and Hereditary Influences
While the exact cause of most congenital heart defects is unknown, genetic predispositions are a significant factor. These can range from large-scale chromosomal abnormalities to single-gene mutations that disrupt heart development during early pregnancy.
One of the most well-documented genetic links to CHD is a chromosomal abnormality. Down syndrome, caused by an extra copy of chromosome 21 (Trisomy 21), is strongly associated with CHD. Approximately half of all infants born with Down syndrome will also have a heart defect. Other chromosomal conditions like Turner syndrome and Trisomy 18 also carry an increased likelihood of heart malformations.
Beyond large chromosomal changes, specific single-gene mutations have been identified that can cause congenital heart disease. These mutations can be inherited from a parent, even if the parent shows no signs of a heart condition. If a parent or a previous child has a congenital heart defect, the risk for a subsequent child is higher than in the general population. For families with a known history of CHD, genetic counseling is a valuable resource to assess the family’s history, discuss genetic testing, and provide information about recurrence risk.
Maternal Health Conditions
A mother’s health before and during pregnancy can influence fetal development, as certain chronic conditions increase the risk for CHD, particularly if not well-managed. The first eight weeks of pregnancy are a sensitive period for the baby’s heart development.
Diabetes, both pre-existing (Type 1 or Type 2) and gestational, is a notable risk factor. If a mother’s blood sugar levels are consistently high, especially during the first trimester, it can interfere with the formation of the fetal heart. The risk of CHD in infants of mothers with pre-gestational diabetes is several times higher than in the general population.
Another metabolic condition that can impact fetal heart development is phenylketonuria (PKU). This is a rare inherited disorder where the body cannot break down an amino acid called phenylalanine. If a mother with PKU does not follow a strict, low-phenylalanine diet before and during her pregnancy, high levels of this substance can cause serious harm to the developing fetus, including heart defects. Autoimmune diseases in the mother, such as lupus, have also been associated with an increased risk for certain types of CHD.
Pregnancy-Related Exposures
Consumption of alcohol during pregnancy is a well-established risk factor for a range of birth defects, including those affecting the heart. There is no known safe amount of alcohol to consume, and its use can lead to conditions on the fetal alcohol spectrum, which often include heart defects. Similarly, smoking tobacco or being exposed to secondhand smoke during pregnancy is linked to a higher incidence of CHDs. The chemicals in cigarette smoke can reduce oxygen supply to the fetus.
Certain prescription medications are also known to pose a risk. For example, some anti-seizure medications, such as valproic acid, and the acne medication isotretinoin have been associated with an increased risk of heart malformations. It is important for individuals to discuss any medications with their doctor before and during pregnancy. Infections contracted during pregnancy can also be a cause, with rubella (German measles) being a classic example. A rubella infection in the first trimester can lead to a collection of birth defects, with heart problems being a common component.
Prenatal Screening and Detection
Advances in prenatal imaging have made it possible to detect many structural heart problems during pregnancy. This early detection allows medical teams to prepare for the baby’s needs after birth, plan for necessary interventions, and provide support to the family.
The most common tool for prenatal screening is the routine mid-pregnancy ultrasound, typically performed between 18 and 22 weeks of gestation. During this scan, the sonographer examines the baby’s anatomy, including a standard four-chamber view of the heart and its major blood vessels. If this routine scan reveals any findings that raise suspicion of a heart defect, or if the pregnancy is high-risk, a more specialized test may be recommended.
This more detailed examination is called a fetal echocardiogram, a targeted ultrasound that provides a comprehensive view of the fetal heart’s structure and function. A pediatric cardiologist or a maternal-fetal medicine specialist usually performs the test. A fetal echocardiogram may be recommended for a family history of CHD, certain maternal health conditions, or an abnormal finding on a routine ultrasound.
While prenatal screening can detect many significant heart defects, some minor issues or those that develop later in pregnancy may not be identified until after the baby is born.