Down Syndrome (cont.)

Medical Author:

Sietske N. Heyn, PhD

Sietske N. Heyn, PhD

Sietske N. Heyn is a medical writer with a PhD in neuroscience. Dr. Heyn's education includes a BS with honors from the University of Oregon, and a doctoral degree in neuroscience from the University of California at Davis. After completing postdoctoral training at the University of California, San Francisco, and many years of working as a medical writer at the Stanford University Center for Down Syndrome Research, Dr. Heyn now runs her own medical writing business.

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Medical Editor:

David Perlstein, MD, MBA, FAAP

David Perlstein, MD, MBA, FAAP

Dr. Perlstein received his Medical Degree from the University of Cincinnati and then completed his internship and residency in pediatrics at The New York Hospital, Cornell medical Center in New York City. After serving an additional year as Chief Pediatric Resident, he worked as a private practitioner and then was appointed Director of Ambulatory Pediatrics at St. Barnabas Hospital in the Bronx.

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In this Article

• What is Down syndrome?
• What are the chromosome basics of Down syndrome?
• How do the extra genes lead to Down syndrome?
• What are the risk factors for conceiving a child with Down syndrome?
• What are the characteristic features and symptoms of Down syndrome?
• What type of prenatal screening is available for Down syndrome?
• How is the diagnosis of Down syndrome made?
• What about cognitive impairment in Down syndrome?
• What other conditions are associated with Down syndrome?
• How is Down syndrome managed?
• What about early intervention and education for Down syndrome?
• What are the needs of infants and preschool children with Down syndrome?
• How do adolescents with Down syndrome develop?
• What should one expect for adults with Down syndrome?
• Do individuals with Down syndrome work?
• Where can I find clinical trials for Down syndrome?
• Down Syndrome At A Glance
• Where can I find more information about Down syndrome?
• Patient Comments: Down Syndrome - Experience
• Patient Comments: Down Syndrome - Symptoms
• Down Syndrome Index

The diagnosis of Down syndrome can be made before birth using one of several diagnostic tests. These tests carry a small risk of miscarriage.

If Down syndrome is suspected after a child is born, a diagnosis can be made via chromosome analysis.

Amniocentesis is performed between 16 and 20 weeks of pregnancy. During this procedure, a thin needle is inserted through the abdominal wall and a small sample of amniotic fluid is taken. The sample is analyzed for chromosome anomalies.

Chorionic villus sampling (CVS) is done between 11 and 12 weeks of pregnancy. It involves the collection a chorionic villus cell sample from the placenta either through insertion of a needle in the abdominal wall or through a catheter in the vagina. The chromosomes in CVS are analyzed for deviations.

For percutaneous umbilical blood sampling (PUB), fetal blood is taken from the umbilical cord using a needle inserted through the abdominal wall. The blood sample is examined for chromosome abnormalities. It is usually performed after week 18.

The most common condition associated with Down syndrome is cognitive impairment. Cognitive development is often delayed, and all individuals with Down syndrome have mild to severe learning difficulties that last throughout their lives. How the extra chromosome 21 leads to cognitive impairment is not entirely clear. The average brain size of a person with Down syndrome is small and scientists have found alterations in the structure and function of certain brain areas such as the hippocampus and cerebellum. Particularly affected is the hippocampus, which is responsible for learning and memory. Scientists are using human studies and animal models of Down syndrome to find out which specific genes on the extra chromosome 21 lead to different aspects of cognitive impairment.