Trisomy 18, also known as Edwards syndrome, is a type of genetic disorder that’s mainly caused by the presence of part or all of an extra eighteenth chromosome present in an unborn child’s genetic makeup.
Like other trisomies, Trisomy 18 isn’t defined by a single set of characteristics, as the condition is known to affect unborn children in different ways. Some of the most commonly reported characteristics of Trisomy 18 include heart defects, kidney abnormalities, delayed growth, clenched hands and choroid plexus cysts.
Behind the Trisomy
To further explain Trisomy 18, unborn children at conception possess 23 chromosomes from their father and mother. These chromosomes combine to create the child, who normally possess 46 chromosomes (two of each type). These chromosomes also have a specific ‘position’ within the child’s genetic makeup, carrying genetic material.
A trisomy occurs when an unborn child has three chromosomes in one position, instead of the standard two. When this happen, it can cause several complications that can severely impede a child’s growth and development.
Trisomy 18 defines the impairment of the eighteenth chromosome, where three of the eighteenth are present instead of the normal two.
Most babies are diagnosed with Trisomy 18 during prenatal tests, including screening tests and diagnostic tests. When trisomies like Trisomy 18 occur in an unborn child, it typically accounts for all of their cells, meaning that the extraneous chromosome appears in each of those cells. While some might assume that trisomies like Trisomy 18 are hereditary, they’re ultimately not.
Trisomy 18 – The Life Expectancy
Trisomy 18 is known to occur in around 1 out of 2,500 pregnancies, typically resulting in 1 of 7,000 live births. These statistics, as published by many Trisomy 18 resources, also haven’t accounted the amount of still births in the second and third trimester caused by this disorder.
Trisomy 18 is a condition that’s responsible for shortening the lifespan of unborn children. Most babies that develop with Trisomy 18 end up dying before birth. The babies that do make it to birth often live for less than a year.
Therefore, the life expectancy for Trisomy 18 is usually less than one year, as most pregnancies and children (about 5 to 8 percent) born with the condition don’t make it. Interestingly enough, Trisomy 18 is one of three trisomies where babies have made it to a live birth.
There are, however, children that have lived past their first few months of life with Trisomy 18. That accounts for a little under 10 percent of babies, with an even smaller percentage actually surviving into adolescence and even adulthood.
