Hypoplastic left heart syndrome (HLHS) is a problem with the heart's structure that is present at birth (congenital). It is a group of related defects that, together, mean that the left side of the heart is underdeveloped. Normally, oxygen-poor blood is pumped through the right side of the heart to the lungs, where it gains oxygen and returns to the left side of the heart. The oxygen-rich blood is then pumped from the left side of the heart to the rest of the body. At birth, all babies also have two connections, or shunts, between the two sides of the heart; however, within a few days of birth these connections close.
Among people with HLHS, the underdeveloped left side of the heart is unable to provide enough blood flow to the body. The normal shunts present at birth help to direct blood to the body; when these connections close the oxygen-rich blood supply decreases. Thus, babies with HLHS might look normal at birth, but will develop symptoms of HLHS within a few days. These symptoms might include:
- Poor feeding
- Problems breathing
- Pounding heart
- Weak pulse
- Ashen or bluish skin color
CDC estimates that each year about 975 babies in the United States are born with hypoplastic left heart syndrome (HLHS). In other words, each year about 2 out of every 10,000 babies born will be born with HLHS.
Without treatment, babies with HLHS die. Although this defect cannot be corrected, surgeries after birth can create the needed connections, or shunts, to allow the blood to get to the body. The right side of the heart, which normally only pumps blood to the lungs, now must provide the blood flow to both the lungs and the body. This extra work eventually weakens the heart. Children with HLHS require regular follow-up visits with a cardiologist throughout their lives, and can develop problems as they grow.
What causes hypoplastic left heart syndrome?
There is no known cause for hypoplastic left heart syndrome (HLHS). The problem develops before birth when there is not enough growth of the left side of the heart.
We at CDC work with many other researchers to study risk factors that can increase the chance of having a baby with HLHS, as well as outcomes of babies with the defect. Following are examples of what our research has found:
The rate of HLHS has been increasing from year to year.
There is a higher risk for HLHS among White babies than among babies of other races or ethnicities.
No strong link exists between caffeine use by a mother and risk for HLHS.
Multivitamin use by mothers before and during pregnancy can decrease the risk for HLHS.
Can hypoplastic left heart syndrome be prevented?
HLHS is a congenital hear defect, meaning it is present at birth. As such, HLHS cannot be prevented. Even so, mothers can take steps before and during pregnancy to have a healthy pregnancy. Steps include taking a daily multivitamin with folic acid (400 micrograms), not smoking, and not drinking alcohol during pregnancy.
