Definition of Trisomy 18
Trisomy 18 is a genetic disorder in which a person has a third copy of genetic material from chromosome 18, instead of the usual two copies.
Causes, incidence, and risk factors
Trisomy 18 is a relatively common syndrome. It is three times more common in girls than boys. The syndrome is caused by the presence of extra material from chromosome 18. The extra material interferes with normal development.
Signs and tests
Examination of the pregnant woman may show an unusually large uterus and extra amniotic fluid. An unusually small placenta may be seen when the baby is born.
Treatment of children with Trisomy 18 is planned on a case-by-case basis. Which treatments are used depends on the patient’s individual condition.
Fifty percent of infants with this condition do not survive beyond the first week of life. Some children have survived to the teenage years, but with serious medical and developmental problems.
Diana Chambers, MS, EdD, Certified Genetics Counselor (ABMG), Charter Member of the ABGC, University of Tennessee, Memphis, TN. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 8/11/2009