Trisomy is the presence of an additional, or third, chromosome in a human cell that typically has just two chromosomes. This extra chromosome can cause many types of developmental disabilities.

During Trisomy Awareness Month in March, many national family advocacy organizations try to raise awareness about the cause, evaluation and treatment of these genetic disorders, especially trisomy 21, trisomy 18 and trisomy 13.

Trisomy 21 (Down Syndrome)

Down syndrome, or trisomy 21, is the most common chromosome abnormality in humans. About 1.4 per 1,000 babies born in the United States each year are found to have Down syndrome, which is generally characterized by physical growth delays, certain facial characteristics and mild to severe intellectual, speech, language and hearing deficits.

Trisomy 18 (Edwards Syndrome)

Trisomy 18, or Edwards syndrome, occurs in about 1 of every 6,000 live births in the United States. Children born with Edwards syndrome may have some or all of the following medical problems:

  • Kidney malformations
  • Structural heart defects at birth
  • Esophageal atresia (a disorder of the digestive system in which the esophagus does not develop properly)
  • Intellectual disability
  • Developmental delays
  • Growth deficiency
  • Feeding difficulties
  • Breathing difficulties
  • Arthrogryposis (a muscle disorder that causes multiple joint contractures at birth, resulting in a loss of motion in the affected joints)
  • Small head (microcephaly)
  • Abnormally small jaw (micrognathia)
  • Cleft lip/cleft palate

Trisomy 13 (Patau Syndrome)

Patau syndrome, or trisomy 13, is found in somewhere between 1 in 10,000 and 1 in 21,700 live births. Many infants have difficulty surviving due to severe neurological problems or complex heart defects, and more than 80% die within their first year of life. Surgery may be necessary to repair visual, spinal or palatal defects (such as cleft palate).

Therapies Can Help

Physical, occupational and speech therapy help individuals with these syndromes reach their full developmental potential, starting with early intervention and continuing throughout the lifespan in educational and vocational settings.

The Mount Sinai Health System provides such therapy services at multiple hospital locations.

For More Information

For additional information please visit:

Down Syndrome Consortium Website
Support Organization for Trisomy (SOFT)

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