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  • What is hypoplastic left heart syndrome?
    • Hypoplastic (pronounced hi-puh-plas-tik) left heart syndrome (HLHS)) is an underdeveloped left side of the heart that is present at birth (congenital). The underdevelopment causes a decrease in blood flow throughout the body. Thus, babies with HLHS might look normal at birth, but will develop symptoms within a few days.

      CDC estimates that each year about 975 babies in the United States are born with HLHS. In other words, each year about 2 out of every 10,000 babies born will be born with HLHS.

  • What are the symptoms of hypoplastic left heart syndrome?
    • Although a baby with HLHS may look normal at birth, symptoms that may appear are:
      * Poor feeding
      * Problems breathing
      * Pounding heart
      * Weak pulse
      * Ashen or bluish skin color

  • 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.

      CDC works 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 relevant research findings:
      * The rate of HLHS has been increasing over time.
      * 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 heart 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.

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Last Revised: January 28, 2014


Data Query

Hypoplastic Left Heart Syndrome Data Query

Access the hypoplastic left heart syndrome data in the WI EPHT online database. Review the Data Details below to learn about interpreting the data.

The WI EPHT website has data about other birth defects:

Data Details

What is the data source?

The website provides data from the Wisconsin Birth Defects Registry, which is maintained by the Birth Defect Prevention and Surveillance program, Wisconsin Department of Health Services.

How does WI EPHT measure birth defects?

The WI EPHT website includes the following measures:

  • Prevalence rate of live births by geography
  • Number of birth defects by geography

What are some considerations for interpreting the data?

While significant effort is made to ensure the accuracy and completeness of the data, there are limitations that are listed below:

  • The Wisconsin Birth Defects Registry does not currently receive reports from all providers in the state. Thus, the numbers presented here represent only a subset of the actual cases.
  • Reporters have up to two years to provide data to the registry, so some cases from the most recent years may not yet be included in the registry.

There are many factors that can contribute to a disease and should be considered when interpreting the data. Some of these include:

  • Demographics, e.g., race, gender, age
  • Socioeconomic Status, e.g., income level, education
  • Geographic, e.g., urban vs. rural
  • Changes in the medical field, e.g., diagnosis patterns, reporting requirements