Health Information

Trisomy 18

Trisomy 18


Edwards syndrome

Trisomy 18 is a genetic disorder in which a person has a third copy of material from chromosome 18, instead of the usual two copies.

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  • Causes

    Trisomy 18 occurs in 1 in 6,000 live births. It is three times more common in girls than boys.

    The syndrome occurs when there is extra material from chromosome 18. The extra material affects normal development.

  • Symptoms

    • Clenched hands
    • Crossed legs
    • Feet with a rounded bottom (rocker-bottom feet)
    • Low birth weight
    • Low-set ears
    • Mental delay
    • Poorly developed fingernails
    • Small head (microcephaly)
    • Small jaw (micrognathia)
    • Undescended testicle
    • Unusual shaped chest (pectus carinatum)
  • Exams and Tests

    An exam during pregnancy may show an unusually large uterus and extra amniotic fluid. There may be an unusually small placenta when the baby is born.

    A physical exam of the infant may show unusual fingerprint patterns. X-rays may show a short breast bone. Chromosome studies will show trisomy 18, partial trisomy, or translocation.

    Other signs include:

    • Hole, split, or cleft in the iris of the eye (coloboma)
    • Separation between the left and right side of the abdominal muscle (diastasis recti)
    • Umbilical hernia or inguinal hernia

    There are often signs of congenital heart disease, such as:

    • Atrial septal defect (ASD)
    • Patent ductus arteriosus (PDA)
    • Ventricular septal defect (VSD)

    Tests may also show kidney problems, including:

    • Horseshoe kidney
    • Hydronephrosis
    • Polycystic kidney
  • Treatment

    There are no specific treatments for trisomy 18. Which treatments are used depend on the patient's individual condition.

  • Support Groups

  • Outlook (Prognosis)

    Half of infants with this condition do not survive beyond the first week of life, and 90% of the children will die by one year of age. Some children have survived to the teenage years, but with serious medical and developmental problems.

  • Possible Complications

    Complications depend on the specific defects and symptoms.

  • When to Contact a Medical Professional

    Genetic counseling can help families understand the condition, the risks of inheriting it, and how to care for the patient.

  • Prevention

    Tests can be done during pregnancy to find out if the child has this syndrome.

    Genetic testing is recommended for parents who have a child with this syndrome and who want to have more children.

Related Information



Summar K, Lee B. Cytogenetics. In: Kliegman RM, Stanton BF, St. Geme JW III, Shor NF, Behrman RE, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 76.


Review Date: 9/8/2013  

Reviewed By: Chad Haldeman-Englert, MD, FACMG, Wake Forest School of Medicine, Department of Pediatrics, Section on Medical Genetics, Winston-Salem, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.

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