Karyotyping is a test used to identify chromosome abnormalities as the cause of malformation or disease. The test can be performed on a sample of blood, bone marrow, amniotic fluid or placental tissue.
When doctors study a human karyotype they look for some significant features, such as if the 46 chromosomes are present, the presence of the two identical chromosomes and 2 sex chromosomes and if there are any missing or rearranged chromosomes.
In Edwards Syndrome, an extra chromosome 18 is indicated, equalling Trisomy 18.
The history of Edwards Syndrome comes from a gentleman named John Hilton Edwards. He first recorded its details afterpublications of a letter he wrote suggesting that antenatal detection of hereditary disorders could be achieved by application of the linkage principle to test material obtained by amniocentesis. Amniocentesis had just been introduced for detection of Rh hemolytic disease of the fetus. He learned about chromosomes from Charles Ford and David Harnden at Harwell.
Pediatrics was Mr. Edwards specialty and he was spending a morning a month at the Children’s Hospital in Birmingham when he recognized a potential chromosomal aberration in a newborn—he called it “trisomy, type unknown.” He obtained postmortem tissues and delivered them to Harwell, where Harnden demonstrated trisomy 18, or Edwards syndrome, as it came to be known. Discovered and named for him in 1960.
In Edward's syndrome there is an extra chromosome-18 (trisomy-18). It is a very serious abnormality that leads to severe mental and growth retardation, abnormalities in the heart and other organs and malformed features that include a small chin, low ears, cleft palate, a webbed neck, and flexed limbs that have deformed hands and feet. These babies do not survive very long and the majorities don't make it past six months of age. Sadly, nothing can be done to change this.
Trisomy 18 occurs in approximately one in 3,000 newborns. In fact, this disorder is ranked second after the Down syndrome in regard to the frequency of its occurrence. At the same time, Edwards Syndrome affects rather girls than boys. The age of a mother can be a risk factor of the development of Edwards Syndrome. Women older than their early thirties have a greater risk of conceiving a child with Trisomy 18, though it can occur in younger women as well.
The physical appearance of the child at birth will suggest the diagnosis of Trisomy 18. However, most babies are diagnosed before birth by amniocentesis. Ultrasounds of the heart and abdomen can detect abnormalities, as can x-rays of the skeleton. Parents can consider the option of a termination of pregnancy. Amniocentesis carries some risk of inducing a miscarriage, so it is usually only recommended when it's thought there might already be some chance of chromosomal abnormality.
The Ethical Issue
Edwards Syndrome, being incurable, raises a number of ethical issues. The termination of pregnancy or abortion is probably the most significant one. Parents of a baby with Edwards Syndrome may suffer from psychological trauma, especially if they observe their baby suffering and agonizing under the impact of Edwards Syndrome for days or probably months.
On the other hand, it is possible to argue that children with Edwards Syndrome can live for sometime making their lives valuable and worthy. Personally, this is a matter that involves mom and dad only and I choose to stay out of the debate of right or wrong. I have been fortunate never to have had to make this choice but certainly it comes down to quality of life and the overall respect of the families decision. Morally the obligation to prevent needless suffering justifies the prevention of the births of disabled neonates.
We live in a world of judgment and criticism and therefore I again stress, the choice is personal.
Medical care for individuals with Trisomy 18 is supportive, and focuses on providing nutrition, treating infections, and managing heart problems. During the first months of life, infants with Trisomy 18 require skilled medical care. Due to the complex medical problems, including heart defects and overwhelming infections, most infants have difficulty surviving to age 1 year. Advances in medical care over time will hopefully help more infants with Trisomy 18 live into childhood and beyond.
Edwards JH, Harnden DG, Cameron AH. A new trisomic syndrome. Lancet i: 787-90.