The human heart develops very early in the pregnancy, between the third and seventh weeks. The developing heart functions like a small adult heart by the eighth week of pregnancy. In most cases Congenital Heart Defects occur due to a developmental error in the formation of the heart.
In its developmental stage the heart begins as a simple hollow tube which grows longer and begins to bend and twist. The entry end of the tube eventually becomes the collecting chambers known as the Right Atrium and Left Atrium. A partition forms to separate these chambers. However there is always a hole in this partition (Septum) while the baby is in the womb. The blood has to flow across the hole until the baby is born.
The middle section of the primitive tube becomes the "pumping chambers" - or Ventricles. It has to form Valves and a dividing Septum. There can be holes in this Septum up to and after the time of birth, but some can still close spontaneously.
The exit end of the Mitral tube separates into the "Great Arteries" - the Aorta and Pulmonary Artery. These are destined to take blood to the body and lungs respectively.
Infections and drugs may be the cause in some cases of Congenital Heart Defects. Contraction of German Measles (Rubella) during the first trimester of pregnancy has been associated with Congenital Heart Defects. The consumption of too much alcohol in early pregnancy may cause heart defects as well as other birth defects. Heredity plays only a small part, and it is unusual for families to have another child with a Congenital Heart Defect. In the majority of cases, we do not know what causes Congenital Heart Disease.
Last Updated: December 2003
Last Reviewed: December 2003
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