If you are a mother-to-be, your doctor may have told you about an 'NT scan', or 'first-trimester screening'. Hearing this name can make you feel a little scared and curious. But it is actually a very simple test, and there is nothing to be afraid of. In this article, we will talk about everything you need to know about this NT scan.
What exactly is an NT scan?
Simply put, an NT scan is a special ultrasound scan that is done during the first three months of your pregnancy, between weeks 11 and 14. The full name of this is the Nuchal Translucency scan. It mainly looks at the risk of your baby having certain genetic conditions, such as Down syndrome.
Often, this scan is accompanied by several other blood tests. These blood tests look at the levels of certain hormones and proteins in your blood. For example:
- Free beta- Human Chorionic Gonadotropin (b-hCG)
- Pregnancy-associated plasma protein-A (PAPP-A)
- Alpha-fetoprotein (AFP)
These hormones and proteins are present in every pregnant woman's body. But if the baby has a condition like Down syndrome , their levels may be lower or higher than normal. When the NT scan and these blood tests are done together, we call it 'combined first-trimester screening' . The results are more accurate when they are done together.
What exactly does this scan look for?
This is a very interesting thing. Every baby growing in the womb has a thin membrane under the skin at the back of their neck, filled with a little fluid. We call this the 'nuchal fold'. This is something that every healthy baby has.
However, in babies with certain genetic conditions, more fluid than normal accumulates in this 'nuchal fold'. Then that membrane becomes a little thicker. The NT scan measures that thickness.
Based on this thickness, it is possible to estimate the risk of the baby having a certain genetic condition.
| Condition Screened | Simple Explanation |
|---|---|
| Down syndrome (Down syndrome / Trisomy 21) | A condition in which our cells have an extra copy of chromosome 21, or three copies, instead of the two that we normally have in our cells. This can affect intellectual and physical development. |
| Trisomy 13 and 18 | This is similar to Down syndrome. Here, there is an extra copy of chromosome 13 or 18. These are conditions that cause very severe birth defects. |
| Turner syndrome | A condition that only affects female babies who carry the X chromosome. In this case, part or all of the X chromosome is missing. This can cause developmental problems and heart problems. |
| Congenital heart disease | Certain heart defects are present at birth. Some can be life-threatening, while others may cause no problems at all. |
But it's important to remember this: The NT scan is a screening test , not a diagnostic test . That means it doesn't 100% guarantee that your baby has these conditions. It only shows whether the risk of developing such a condition is high or low.
In addition to this main point, the doctor will pay attention to several other things when performing this scan.
- Is your baby growing properly?
- How many babies are there in the womb?
- If they are twins, do they share the same placenta?
- Make sure you know exactly how long you are pregnant .
What happens during an NT scan?
This is a normal scan like any other scan you have had before. Nothing special. You will be asked to drink 2 to 3 glasses of water about an hour before the scan. The reason for this is that it is easier to see the baby clearly when your bladder is full. So do not urinate before the scan. Although it may feel a little uncomfortable, it will help the scan to go well.
When you go into the scan room, you will be asked to lie down on a bed. The technician will then apply a small amount of gel to your lower abdomen and pass a small instrument (wand/probe) through it to take pictures. You will feel a slight pressure at this time, but it will not be painful . Once the necessary pictures have been taken, the scan is over. You can go home as usual.
Is it necessary to have this scan?
No. The NT scan is not a mandatory test. It is completely optional. This means that you have the full right to decide whether or not to have it.
Some parents like to do this test and find out about their baby's health risks in advance. That way, if there is a child with special needs, they have time to prepare mentally and in every other way to care for that child.
Also, some parents feel that such a test can cause unnecessary stress. They may decide not to have the test if the results do not change the way they care for their child. Both decisions are correct. The important thing is that you and your partner make the decision that is best for you, together with your doctor if necessary.
How to understand the scan results?
As the baby grows in the womb, the nuchal fold we talked about earlier also gradually increases in thickness. Therefore, the measurement obtained during the scan is compared with the average measurement of other healthy babies of the same age.
| Result | Description |
|---|---|
| Average result (Low Risk) | It is considered normal for the measurement to be up to 2 millimeters (2mm) at 11 weeks and up to 2.8 millimeters (2.8mm) at 13 weeks and 6 days. This means that the baby is at low risk of having a genetic condition. |
| Abnormal result (High Risk) | If the measurement is above the normal range mentioned above, it is considered a "high risk" result. This does not mean that the baby has a disease, but only that the risk is higher than normal. |
Your doctor will use not only this scan measurement, but also your age and blood test results to make a final diagnosis. When combined, the NT scan and blood test can predict the risk of genetic conditions with about 85% accuracy .
However, there is a 5% chance of a "false positive" result. This means that the baby may be at higher risk, even if there are no problems.
What to do if the NT scan results are abnormal?
First of all, don't panic . A 'high risk' result doesn't necessarily mean there's a problem with the baby. It just means that further testing is needed.
Your doctor will suggest further tests that you can have. These tests can make a 100% accurate diagnosis.
- Chorionic Villus Sampling (CVS): Here, a very small piece of tissue is taken from the placenta and examined.
- Amniocentesis: This involves taking a small sample of the amniotic fluid in the uterus and testing it.
- Prenatal cell-free DNA (cfDNA) screening: This is a simple blood test that analyzes fragments of your baby's DNA in your blood to screen for genetic conditions. ( This is a simple blood test that analyzes fragments of your baby's DNA in your blood to screen for genetic conditions.)
Your doctor will explain the pros, cons, and risks of each of these tests to you, tailored to your situation. Then, you can decide whether or not to have them.
Take-Home Message
- An NT scan is a completely safe and painless ultrasound test performed during the first trimester of pregnancy.
- It is not mandatory to do this. It is entirely up to you.
- This tests for the risk of genetic conditions such as Down syndrome, but does not confirm the presence of the disease.
- If you receive a 'high risk' result, don't panic, but talk to your doctor for further testing.
- Never hesitate to discuss and clarify all your problems and doubts with your doctor.
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