You may have heard the word "Trisomy" or your doctor may have mentioned it. It's normal to feel a little scared and curious when you hear this. What is trisomy? Why does it happen? How will it affect the baby? Let's talk about it all in a simple way that you can understand.
What is Trisomy? In simple terms...
Imagine that our body is made up of millions of tiny cells. Inside each cell, there is a place like the control center of that cell, which we call the nucleus . Inside that nucleus are things called `Chromosomes` . These are like books. Everything about our body, every characteristic that makes us different from others (such as height, color, hair color, eye color) is written in these books called chromosomes. This information is what we call `DNA` .
Normally, every cell in a healthy person has 23 pairs of these chromosomes. That's a total of 46 chromosomes. Half of these, 23, come from our mother, and the other half, 23, come from our father.
Now, here's what trisomy means: Sometimes, in addition to one of those chromosome pairs, an extra chromosome is added. Then the total number of chromosomes becomes 47 instead of 46. "Tri" means three, and "somy" means something like a body. So, trisomy is simply having three chromosomes where there should be two.
Although a baby with this extra chromosome can be born full-term, it can sometimes cause a miscarriage in the first three months of pregnancy.
What are the main types of trisomy?
Doctors diagnose this trisomy condition based on which chromosome pair the extra chromosome is in. Because each chromosome pair has a specific role in our body, the genetic condition of the baby will vary depending on where the extra chromosome is added.
The most common trisomy conditions are:
- Trisomy 21 : This is the condition we all know as Down syndrome . There is an extra chromosome in the 21st chromosome pair.
- Trisomy 18 : This is also called Edward syndrome .
- Trisomy 13 : This is called Patau syndrome .
Similarly, the 23rd pair of chromosomes in our genetic makeup determines our sex. These are called `XX` for a female and `XY` for a male. When cells divide, abnormalities in these sex chromosomes can also occur, resulting in trisomies. Examples of these are:
- Trisomy X (`Trisomy X` or `XXX`)
- Klinefelter syndrome (`Klinefelter syndrome` or `XXY`)
- Jacob's syndrome (`Jacob's syndrome` or `XYY`)
Who is most likely to be affected by this trisomy condition?
In fact, trisomy can occur at any stage of pregnancy. However, it has been found that the risk is slightly higher when women over the age of 35 become pregnant . However, surprisingly, most babies born with trisomy are born to parents under the age of 35. This is because, statistically speaking, more babies are born to people under the age of 35.
The most important thing: Trisomy is not something that happens through the fault of the mother or the father. It is a genetic change that occurs randomly.
How common is trisomy?
The most common type of trisomy is trisomy 21, or Down syndrome. For example, in the United States alone, about 6,000 babies are born with Down syndrome each year. That's about one in every 700 babies.
What are the symptoms of trisomy during pregnancy?
During your pregnancy ultrasound scan , your doctor will look for signs of trisomy. Some of the signs include:
- The amount of water around the baby (amniotic fluid) is very small.
- The baby's umbilical cord has only one artery instead of the usual number of arteries.
- Placenta smaller than normal.
- The baby's movements (squirming) seem to be less.
- The baby looks smaller than his or her actual age.
- Some physical abnormalities, for example, certain heart problems or a cleft palate.
What are the symptoms after the baby is born?
The symptoms a baby may experience may vary depending on the type of trisomy. Some common symptoms include:
- Being shorter than normal (short stature).
- A round face and a flat face.
- A slanted look on the eyes.
- Cleft palate.
- Malformation of internal organs (such as the heart, lungs, kidneys) or problems with their function.
- Developmental delays and intellectual disabilities.
Why does this trisomy occur? A very scientific explanation...
The chromosomes in our bodies are made in a very specific order. This sequence of cells is like the "blueprint" of who we are. When the cells of the reproductive organs are made (sperm in men, eggs in women), they start with a single fertilized cell. This cell then undergoes a process called meiosis . This is where one cell divides twice, producing four cells. Each new cell has half the amount of DNA in the original cell, or 23 chromosomes.
During the process of cell division (meiosis) , sometimes cells don't divide properly. When that happens, an extra copy of a chromosome comes along and joins a pair of chromosomes. Normally, there should be two chromosomes in each pair. But here, a third chromosome is added to that pair. That's called trisomy.
Trisomy occurs at the time of fertilization . This is a random event, not caused by anything the mother did during pregnancy. However, as mentioned earlier, the risk is slightly higher for those who become pregnant after the age of 35.
How is trisomy diagnosed?
Genetic testing during pregnancy can provide clues about the presence of trisomy. After the baby is born, the condition is confirmed by a physical examination and another genetic chromosome test using a blood sample from the baby.
What tests are used to diagnose trisomy?
During pregnancy, your doctor will likely order a blood sample from your mother and a scan. As mentioned earlier, the scan will look for things like excess fluid around the baby, a nuchal lucency , and the length of the baby's limbs. These could be signs of a genetic abnormality.
After these basic tests, there are more specific tests to confirm the condition:
- Chorionic villus sampling (CVS): Between 10 and 13 weeks of pregnancy, a small sample of cells is taken from the placenta to test for genetic conditions and the baby's sex.
- Amniocentesis: Between 15 and 20 weeks of pregnancy, a small sample of the amniotic fluid surrounding the baby is taken to check for possible health problems.
- Percutaneous umbilical blood sampling (PUBS): A small sample of blood is taken from the baby's umbilical cord to check the baby's health.
- Non-invasive prenatal testing (NIPT): After 10 weeks of pregnancy, a blood sample from the mother is tested to assess whether the baby has any genetic abnormalities.
How are trisomy conditions treated?
Trisomy is a lifelong condition. Therefore, long-term treatment is required to relieve the symptoms associated with this condition. Treatments for children born with trisomy include:
- Surgery to correct physical abnormalities.
- Providing educational support .
- Speech, behavioral and physical therapy .
- Medications to control symptoms of other medical conditions that may develop over time.
Is there a way to reduce the risk of trisomy?
In fact, genetic conditions like trisomy cannot be prevented. Because the chromosomal defect occurs randomly during cell division, you can reduce your risk of having a child with a genetic condition by doing the following:
- Understanding the risks of pregnancy if you are over 35.
- Genetic screenings before pregnancy.
- Avoiding the use of tobacco products and alcohol.
- Take care of your health by eating a well-balanced diet and exercising regularly.
How will this trisomy affect my baby?
Because the extra chromosome changes the baby's "blueprint," it can cause birth defects ( such as distinctive facial features) and intellectual disabilities. Many children born with trisomy 12 will develop other health problems (such as frequent ear infections, heart disease, and sleep apnea) after the condition is diagnosed. However, with proper treatment, your child can live a happy, fulfilling life .
However, babies born with conditions such as Trisomy 18 or Trisomy 13 have a lower chance of surviving beyond the first few weeks of life (the neonatal period) due to the severity of the condition (especially delays or abnormalities in organ development). Your doctor will assess your baby's health and provide treatment to increase the chances of survival for babies born with these conditions.
When should I see a doctor?
One side effect of trisomy is the risk of miscarriage . This usually occurs during the first three months of pregnancy. If you have any of the symptoms of miscarriage (listed below), see your doctor immediately:
- Lower abdominal pain, cramping.
- Lower back pain.
- Abdominal pain.
- Slight or heavy bleeding.
- Having a cold and getting a fever.
What are the important questions to ask the doctor?
If you have any more questions about this, don't be afraid to ask your doctor. Here are some questions you can ask:
- How can I reduce the risk of having a child with a genetic condition like trisomy?
- What prenatal tests do you recommend to confirm if my baby has a genetic condition?
- Can I have a successful pregnancy after being diagnosed with a trisomy?
What is the difference between Trisomy and Monosomy?
Both of these are genetic conditions.
- Trisomy is the presence of an extra copy of a chromosome.
- Monosomy is the absence of one copy of a chromosome (i.e., the loss of one chromosome).
Both of these genetic conditions occur as a result of a genetic mutation that occurs during cell division. This abnormality cannot be prevented from occurring during cell division.
What to remember from what we have discussed (Take-Home Message)
Since there is no way to prevent genetic abnormalities like trisomy, if you are planning to become pregnant, talk to your doctor about genetic testing to assess your risk of having a child with a genetic condition.
If you are diagnosed with a trisomy condition while you are pregnant, don't panic. There is a lot of support and resources available to help you and your baby live healthy, fulfilling lives. Genetic counseling can help you understand your baby's condition and provide the care and support they need as they grow. Remember, you are not alone.
` Trisomy, chromosomes, genes, Down syndrome, pregnancy, genetic testing, Patau syndrome, Edward syndrome
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