Edward’s Syndrome, termed medically as Trisomy 18 is a type of birth defect caused due to the presence of added genetic material i.e. a third copy of the chromosome 18 instead of the natural 2 copies. It is the second-most common birth defect after Trisomy 21, i.e. Down’s Syndrome. Babies born with this added genetic material often has several internal and external physical deformities. Also Read: Hirschsprung Disease: Causes, Symptoms And Treatment
Named after the English geneticist John Hilton Edwards, who first described the syndrome in 1960, the Trisomy 18 is quite a rare type of defect, i.e. about 1 in every 5000 babies and is more commonly seen in case of a girl child.
Chromosomes are the threadlike structures present in cells that help to keep genes intact. These genes or genetic material usually carries the commands or instructions needed to make every part of a baby's body. During the formation of a zygote, when the egg and sperm join, 23 chromosomes from both the egg and sperm fuse to make a foetus which now has a total of 46 chromosomes. When either of the parents carries a wrong number of chromosomal materials, the defect is passed on to the foetus, which now has a wrong number of chromosomes.
A trisomy usually signifies that the baby chiefly has an extra chromosome in one or more body cells. In case of Trisomy 18 or Edward’s syndrome, the baby has 3 copies of the chromosome 18 which may ultimately lead to several abnormalities.
There are three types of trisomy 18:
Full Trisomy 18:
Being quite a common type of trisomy, where there are extra chromosomes in all the cells of the baby’s body.
Mosaic Trisomy 18:
A rare type of trisomy, where the extra chromosome 18 is only in few of the cells.
Partial Trisomy 18:
In partial trisomy, the baby has only one part of the chromosome 18, i.e. the extra part of the chromosome 18 is attached to any other chromosome of the egg or sperm.
With the advanced technology, in today’s time, there are imaging techniques to diagnose the symptoms of this defect within the uterus itself when the foetus is very small. In most cases, the survival chance of the foetus with Edward’s syndrome is small to nil. Those babies who survive are born with the characteristic features which include:
- Cleft palate
- Microcephaly (small and abnormally shaped head)
- Micrognathia (abnormally shaped small jaw and mouth)
- Clenched fists with overlapping fingers that are hard to straighten
- Defects of the heart, lungs, stomach/intestines and kidneys. Also Read: Genetic Issues May Lead To Congenital Heart Disease
- Clubbed feet and crossed legs
- Feeding problems
- Low-set ears
- Umbilical hernia
- Chest deformity
- Arched or short spine
- Slowed growth
- Weak cry
Diagnosis And Treatment
A routine prenatal screening or ultrasound is done throughout the 18th to 20th week of pregnancy which usually helps in discovering the various above-mentioned signs of the syndrome. Once, the doctor notices any abnormality in the diagnosis, genetic testing can be done to authenticate the presence of abnormal genetic material.
Tests such as Amniocentesis and Chorionic villus sampling (CVS) tests are generally considered safe and can help in the prenatal genetic diagnosis of the foetus.
The abnormalities associated with Trisomy 18 or Edward’s syndrome are so severe that most women often suffer a miscarriage or if the babies are born, they often die within the first year after birth. The ones who ultimately survive this chronic syndrome suffer from severe mental and physical development issues.
Till date, there is no cure for this condition, treatment options usually consist of offering the child palliative and supportive care throughout life to bestow the best quality of life possible.