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  • What is a Down Syndrome?
    • Down syndrome is a condition in which a baby is born with an extra chromosome. Chromosomes are small “packages” of genes in the body. They determine how a baby’s body forms during pregnancy and how the baby’s body will function after birth. Normally, a baby is born with 46 chromosomes. Babies born with Down syndrome have an extra copy of one of these chromosomes. This extra copy changes the body and brain’s normal development and causes mental and physical problems for the baby.

      Even though people with Down syndrome might have some common physical and mental features, symptoms of Down syndrome can range from mild to severe. Usually, mental development and physical development are slower in people with Down syndrome than in those without it.

      Some common physical signs of Down syndrome include:
      * A flat face with an upward slant to the eye, a short neck, small ears, and a large tongue
      * Tiny white spots on the iris (colored part) of the eye
      * Small hands and feet
      * A single crease across the palm of the hand
      * Small pinky fingers that sometimes curve toward the thumb
      * Poor muscle tone or loose ligaments

      CDC estimates that each year about 3,357 babies, or 13 of every 10,000 babies, in the United States are born with Down syndrome.

  • What problems do children with Down syndrome have?
    • Babies and adults with Down syndrome can have physical problems, as well as intellectual disabilities. Every baby born with Down syndrome is different. In addition to the physical signs, some might have major birth defects or other medical problems. However, many people with Down syndrome live happy, productive lives well into adulthood.

      Still, some physical problems associated with Down syndrome include:
      * A birth defect of the heart
      * Stomach problems, such as a blocked small intestine
      * Celiac disease, a digestive disease that damages the small intestine so that nutrients from food are not absorbed well
      * Problems with memory, concentration, and judgment, often called dementia
      * Hearing problems
      * Eye problems, such as cataracts or trouble seeing objects that are close by (far-sighted)
      * Thyroid problems
      * Skeletal problems

      A person with Down syndrome can have an IQ in the mild-to-moderate range of intellectual disabilities.S/He also might have delayed language development and difficulties with physical coordination.

  • What causes Down Syndrome?
    • To understand Down syndrome, it is necessary to understand how a baby develops. Each baby starts developing when he or she receives 23 chromosomes from the mother’s egg and 23 chromosomes from the father’s sperm. The combine to form a total of 46 chromosomes that will be present in every cell of the new fetus’ body. When a baby has Down syndrome, an error happened when either the egg or the sperm was formed. This error caused an extra chromosome (called chromosome number 21) in the egg or sperm, so that the baby received a total of 24 instead of 23 chromosomes from one of its parents. Therefore, the baby ends up having 47 chromosomes in every cell of his or her body, instead of 46. This extra chromosome causes the physical signs and additional problems that can occur among people with Down syndrome. The causes for the extra chromosome are not yet known.

      The age of the mother is the only factor that has been shown to increase the risk of having a baby with Down syndrome. This risk increases with every year, especially after the mother is 35 years of age.

      Mother’s Age Risk of Having a baby with Down Syndrome
      25 years 1 in 1,250
      30 years 1 in 1,000
      35 years 1 in 400
      40 years 1 in 100
      45 years 1 in 30

      Even though the risk increases with age, older women have fewer babies than younger women. Because younger women are more likely to have babies than older women, 80% of babies with Down syndrome are born to women younger than 35 years of age. (, August 26, 2010.)

      CDC works with many researchers to study the risk factors that can increase the chance of having a baby with Down syndrome. Following are examples of what this research has found:
      * The number of babies with Down syndrome seems to be increasing, especially among mothers older than 35 years of age.
      * Certain factors seem to influence how long a person with Down syndrome will live, including ethnicity, low weight at birth, and whether the baby was born with a heart defect.
      * Death rates among Black or African-American infants with Down syndrome seem to be higher than death rates among White infants with Down syndrome.

  • Can Down Syndrome be prevented?
    • There is no known way to prevent Down syndrome. However, infants and children with Down syndrome often will benefit from special programs that help to improve their physical and mental functions. These include speech therapy, occupational therapy, and exercises for physical coordination. Children with Down syndrome usually need extra help or attention in school.

      While there is currently no way to prevent Down syndrome, 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

Down Syndrome (Trisomy 21) Data Query

Access the Down Syndrome data in the WI EPHT online database. Review the Data Details below to learn about interpreting the data.

The WI EPHT online data 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