Edwards Syndrome, also known as Trisomy 18, is a genetic disorder caused by the presence of a third copy of all or part of chromosome 18. This causes abnormal development in many of the baby’s organs. About 1 in every 6,000 babies is born with Trisomy 18, and most are female.
There are three types of Edwards Syndrome, Trisomy 18:
- Full Trisomy 18. The extra chromosome is in every cell in the baby’s body. This is the most common type of Trisomy 18.
- Partial Trisomy 18. The child has only part of an extra chromosome 18. That extra part may be attached to another chromosome in the egg or sperm. This type of Trisomy 18 is very rare.
- Mosaic Trisomy 18. The extra chromosome 18 is only in some of the baby’s cells. This form of Trisomy 18 is also rare.
Women of all ages can have a child with Trisomy 18, however the chance increases as a woman gets older. A first trimester screening that includes a blood test and ultrasound offers early information about a baby’s risk of having Trisomy 18. A second trimester blood test called a quad screen can also aid in early detection. More precise methods take cells from the amniotic fluid (amniocentesis) or placenta (chorionic villus sampling) and analyze the chromosomes to confirm diagnosis.
Individuals with Trisomy 18 often suffer from intrauterine growth retardation and subsequently, low birth weight. Some features of Trisomy 18 include having a small, abnormally shaped head, small jaw and mouth, clenched hands and fists with overlapping fingers, rocker bottom feet, cleft lip and palate, groin hernia, birth defect with intestinal organs outside of the body, kidney defects, heart defects, low-set ears, single line palms and drooping of the upper eyelid. There is no cure or treatment for Trisomy 18 and many babies don’t survive past the second or third trimester of pregnancy.
Due to several life-threatening medical problems, many babies with Trisomy 18 don’t survive birth. About half of babies who are carried full-term are stillborn. Boys with Trisomy 18 are more likely to be stillborn than girls. Babies who survive birth usually die within their first month of life. Only five to 10 percent of children with Trisomy 18 live past their first year of life but with severe intellectual disabilities.
In the United States, a rare disease is defined as a condition affecting fewer than 200,000 people in the U.S. There are as many as 7,000 rare diseases. The total number of Americans living with a rare disease is estimated at between 25-30 million.
- May involve chronic illness, disability, and often premature death
- Often have no treatment or not very effective treatment
- Are frequently not diagnosed correctly
- Are often very complex
- Are often caused by changes in genes
Source: U.S. National Library of Medicine. Medline Plus. http://www.medlineplus.gov