What in the World is a Trisomy?

My son, age 4, and his sister, Audrey Grace. She was six days old in this picture, the day before she went in for neurosurgery. She was a full term, 5lb, Trisomy 18 baby.

My son, age 4, and his sister, Audrey Grace. She was six days old in this picture, the day before she went in for neurosurgery. She was a full term, 5lb, Trisomy 18 baby.

Simply put, a Trisomy is the presence of a third copy of a particular chromosome. In reality, a trisomy turns your life upside down.

In 1956, it was determined that the human body has 23 pairs of chromosomes. Twenty-two pair, plus your gender chromosomes. In 1959, trisomies were discovered. If there is a third copy of one of the pairs, it is called a Trisomy (remember, “tri” means three). The extra information really confuses the body. It gets all confused and stuff goes wrong.

Trisomy 21 (or a third copy of the 21st chromosome) is also known as Down Syndrome. By syndrome, it means that there is a massive list of things that could go wrong, but the number of things that are actually wrong varies by person, as does the severity of the symptom. For instance, 40% of those with Trisomy 21 have heart problems. Some will have a hole between the upper chambers of the heart; some will have a hole between the lower chambers. That hole can be less than a millimeter or several millimeters. Their heart problem could be something entirely different. Each person is a unique individual with their own set of symptoms, but just one primary cause, that being the third copy of a chromosome. Trisomy 21 is the most common trisomy. 6,000 babies born in the United States each year have Down Syndrome. That means one out of every 700 babies has this trisomy.

Trisomy 18 is the second most common trisomy. That means the extra chromosome is the third copy of the 18th. It is also known as Edwards Syndrome. This trisomy is referred to as being “incompatible with life.” There are about 1000 babies born in the United States each year with Edwards Syndrome. That would mean one of every 6,000 babies born has this extra chromosome. Of those, 50% will not survive for a week and 90% will never see their first birthday. There are also a litany of different issues associated with this syndrome. My daughter was born with a couple loops of intestine in her umbilical cord, had a clubbed foot, a sacral myelomeningocele (an open-to-the-outside neural tube defect on her tailbone), and five heart defects. She underwent six hours of neurosurgery when she was a week old to repair the neural tube defect, which required placing a shunt in her head to drain off excess fluid which would happen after the repair. She was with us for seven days shy of seven months. Many doctors had told us she probably wouldn’t be born alive. We were so blessed to have the time we did.

Trisomy 13 is known as Patau’s Syndrome and is the third most common trisomy, occurring in roughly one of every 10,000 births in the US. More than 80% of Trisomy 13 babies born alive will pass away within the first month. Theirs is also a diagnosis of being “incompatible with life.”

Trisomy 15, 16, 22 as well as extra gender chromosomes (XXX, XXY, XYY) are well known, but trisomies of any chromosome can happen. I have known a mom of a child with Trisomy 8.


Before I had the first indication that anything might be wrong with the little girl I carried, I had never heard of trisomies. While we were awaiting testing, I began to learn about trisomies. After her diagnosis, I continued my learning, focusing on trisomy 18. When she was in the hospital with RSV, I had nurses come in and ask me questions about Edwards Syndrome. It is rare enough that most of them will not have the opportunity to care for a baby with this particular disorder more than a couple of times in their career, if at all. I didn’t have to learn a little bit about every illness, as a medical professional would, so I became their expert on Trisomy 18. I was thankful for them asking. I appreciate people who are willing to learn.

If you have any questions, please leave them in the comments. I am more than willing to help people understand, as far as my knowledge extends. You can also visit websites like SOFT or the Trisomy 18 Foundation. They are a wealth of knowledge and understanding.


Tell us what you think!

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s