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What causes congenital heart disease?

When parents first discover that their child has a heart defect, it is common to ask:


"Why did this happen?"

“Will it ever happen again in our family?”


These same questions arise when a person with congenital heart disease considers having children.

Causes of congenital heart disease:


A congenital heart defect is a heart problem that appears at birth. It is caused by abnormal formation of the heart during fetal development. Congenital heart defects are the most common type of birth defect, affecting 1 in 100 babies. In most cases, when a child is born with a congenital heart disease, and there is no known cause for it


Some of the known causes of congenital heart defects include genetics, environmental factors, and other factors related to the mother's health. In about 8 out of 10 cases, the cause of a congenital heart defect is unknown.  


Most mothers of children born with congenital heart disease will look critically at their children's particular behaviors during pregnancy to try to find a cause for their child's disease.  It's important to remember that most cases of congenital heart disease have no known cause. However, some types of congenital heart defects are known to occur more often when the mother comes into contact with certain substances during the first few weeks of pregnancy, while the baby's heart is developing. It has been proven that some maternal diseases and the medications taken for these diseases affect the development of the heart. Other illnesses or medications seem to have no effect on the baby's heart.


Always consult your doctor for more information.

Most cases of congenital heart disease have no known cause. Some of the known causes of congenital heart disease include:

  • Genetic or genetic causes - 20% of cases have a genetic cause

  • Other birth defects - a baby with certain birth defects, such as Down syndrome, is more likely to have a heart defect

  • Viral infections: such as German measles.

  • Maternal diabetes: insulin-dependent.

  • Environmental reasons: An example of this is exposure to certain types of radiation, or various environmental pollutants during pregnancy.

  • Reasons related to taking some medications: such as anti-seizure medications and some cosmetics that the mother uses during the first period of pregnancy.

  • Unknown reasons: There is still a lot of mystery surrounding the true causes of these distortions

Genes and congenital heart disease

The risk of congenital heart disease increases when one parent has a congenital heart disease, or another sibling is born with congenital heart disease.


If there are no other family members with congenital heart disease, the chance of a congenital heart malformation in a future pregnancy (brother or sister) is very small, about 3-4%, compared to the usual societal risk of about 1%.


If we know the chromosomal or genetic change that caused the heart defect, it may be easier to predict how likely the defect will be in the affected child's brother, sister, offspring or father.


In most cases of congenital heart disease, the cause is unknown and there are limited options for genetic testing.


As children with congenital heart disease enter childbearing age, it is important that they engage in healthy, positive and informed discussions with their parents about the genetic aspects of congenital heart disease, as this can have major implications for future family planning.

How can congenital heart disease be prevented?

Women who are pregnant or planning to become pregnant can take certain precautions to reduce the risk of having a baby with a congenital heart defect:

If you're planning to become pregnant, talk to your doctor about any prescription or over-the-counter medications you're taking.

  • If you have diabetes, make sure your blood sugar levels are under control before you become pregnant. It's also important to work with your doctor to manage the disease during pregnancy.

  • If you haven't been vaccinated against rubella or rubella, avoid exposure and talk to your doctor about prevention options.

  • If you have a family history of congenital heart defects, ask your doctor about genetic testing. Certain genes may contribute to abnormal heart development.

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