Trisomy 18 is a genetic disorder in which a person has a third copy of material from
Causes, incidence, and risk factors
Trisomy 18 is a somewhat common syndrome. 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.
- Crossed legs
- Feet with a rounded bottom (rocker-bottom feet)
Low birth weight
- Low-set ears
- Mental delay
- Poorly developed fingernails
- Small head (
- Small jaw (
micrognathia) Undescended testicle
Unusual shaped chest (
Signs and tests
An exam during pregnancy may show an unusually large uterus and extra
A physical exam of the infant may show unusual fingerprint patterns. X-rays may show a short breast bone.
Other signs include:
Hole, split, or cleft in the iris of the eye (
Separation between the left and right side of the abdominal muscle (
diastasis recti) Umbilical herniaor inguinal hernia
There are often signs of
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 of children with trisomy 18 is planned on a case-by-case basis. Which treatments are used depend on the patient’s individual condition.
- Support Organization for Trisomy 18, 13 and Related Disorders (SOFT) —
- Trisomy 18 Foundation —
- Hope For Trisomy 13 and 18 —
Half 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.
Complications depend on the specific defects and symptoms.
Calling your health care provider
Genetic counseling can help families understand the condition, the risks of inheriting it, and how to care for the patient.
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.