The scan that looks at the water behind your baby's neck: All about Nuchal Translucency!

If you are a mother-to-be, your doctor may have told you about this scan called the `Nuchal Translucency`. You may have even heard about it from a friend. What exactly is this scan? What does it look for? Is it necessary to have it done? You probably have a lot of questions like these. Don't worry, we will explain everything in a simple way that you can understand.

What is Nuchal Translucency?

Simply put, a nuchal translucency is a special ultrasound scan done during the first trimester of your pregnancy. It basically looks at the thickness of the amniotic fluid under the skin at the back of your baby's neck , or how much fluid there is. Did you know that every baby has a small amount of amniotic fluid at the back of their neck, and it's completely normal ?

However, by measuring the amount of this fluid, doctors can get an idea of ​​the risk of the baby having certain chromosomal conditions or genetic changes .

The important thing is that this ``NT`` scan is only a screening test . That is, it does not diagnose the baby with any condition. It only helps your doctor decide if the baby is at risk and if so, whether further testing is needed. Got it?

What does this scan look like?

Okay, now let's see what exactly this `nuchal translucency' scan looks at. With this scan, the doctor looks at the space at the back of the baby's neck called the `nuchal fold.' As I said before, every baby has fluid at the back of their neck. Doctors have found that babies with certain chromosomal or genetic conditions may have more fluid in this part of their neck.

What kinds of situations are you looking at to see if there is a risk?

If the amount of fluid behind the neck is higher than normal, it may indicate that the baby is at risk for developing conditions such as:

• Down syndrome (Trisomy 21) : You may have heard of this. This is the condition that the `NT` scan mainly focuses on.
• Patau syndrome (Trisomy 13)
• Edwards syndrome (Edwards syndrome - Trisomy 18)

These are the main chromosomal abnormalities that are looked for. In addition, an increased `NT` value can be associated with some congenital heart conditions., which means it can also be associated with an increased risk of certain congenital heart problems. So, the results of the `NT` scan can give a rough idea of ​​whether the baby is more or less likely to have these conditions.

Another thing is that during this ``NT`` scan, doctors also check several basic anatomical parts of the baby's developing body. For example, they check whether the baby's skull, brain, limbs, and intestines are developing normally. If other abnormalities are detected during the ``NT`` scan, it can also increase the risk of genetic or structural conditions.

When is the NT scan done?

This is also a problem for many mothers. The `NT` scan is done between 11 weeks and 13 weeks and 6 days of pregnancy. In other words, it is done when the length from the baby's head to the bottom (this is called the `Crown-Rump Length - CRL`) is between 45 and 84 millimeters .

Why is it done at this specific time? The reason is that after 14 weeks, as the baby grows, the fluid behind the neck starts to be absorbed back into the baby's body. Then it is difficult to measure it accurately. That is why doctors recommend getting the ``NT`` scan done within this specific time. This ``NT`` scan is usually done as part of the first-trimester screening test .

What is this first-trimester screening kit?

You may have heard this term before. The ``First Trimester Screening Kit'' (sometimes called ``Combined Sequential Screening'') is a set of tests that assess the baby's risk of developing certain congenital conditions , that is, conditions that are present at birth.

In addition to the NT scan, a blood sample is also taken from you . These blood tests help assess the risk of your baby having congenital conditions. In fact, the results of these blood tests combined with the NT scan alone are much more accurate .

Who needs an NT scan?

The `NT` scan can be done by any pregnant woman , but it should be done between the 11th and 13th weeks mentioned earlier. This is not a mandatory test, it is optional .

However, many doctors recommend this because it can help you identify any risks early on. It's best to talk to your doctor and make a decision based on what each test will look for and the pros and cons.

How is the NT scan done?

This is also very simple. The NT scan is done in the same way as a regular ultrasound scan. Most often, it is an abdominal ultrasound.One is done. However, sometimes, for example, if it is difficult to get a clear image due to the position of your uterus or the baby's position, a scan through the vagina (vaginal ultrasound) may also be done.

Before the scan, the doctor or the scanning technician will apply an ultrasound gel to your abdomen. Then, a small handheld device called a transducer will be moved over your abdomen. The images of your baby will be displayed on a monitor. The thickness of the fluid behind your baby's neck will then be measured in millimeters . You will not feel any pain during this procedure.

How are the results of the NT scan calculated?

The risk is often not calculated based on the value from the NT scan alone. Your doctor will usually add up the results of all your first trimester screenings to calculate your overall risk of your baby having a congenital condition.

I've said before that doing a blood test along with the NT scan increases the accuracy of the results. So, in most cases, the results of both, your age , and perhaps whether the baby's nasal bone is visible (this is also used to see the risk of Down syndrome), are taken into account when giving you a final risk score.

Why are the results called "risk"?

The result you get is usually expressed as a mathematical risk . For example, your result might say "1 in 300 chance." This means that out of 300 babies with the same `NT` score and other test results as you, only 1 in 300 will have the congenital condition.

• If the fluid level is normal : This means that the risk of a congenital condition is low .
• If the amount of fluid is high : It means there is a higher risk of a congenital or genetic condition.

Think about it this way, if you're told that the risk of being hit by a car while you're walking down the street is 1 in 1000, that doesn't mean that you'll definitely get hit. The same goes for this. Even though the risk is high, it doesn't mean that the baby will definitely have a problem.

The important thing is that a doctor will never make a diagnosis based on the results of the `NT` scan. These are only preliminary tests. If the `NT` value is high, your doctor or a genetic counselor will explain to you about additional tests. In many cases, even if the `NT` value is high, it may not be related to a chromosomal or genetic condition. That is why additional tests are always recommended.

How accurate is the NT scan?

If you do the `NT` scan alone, it will detect conditions like `Down syndrome (Trisomy 21)` in about 70% of cases.It can be detected. However, many doctors combine the ``NT`` scan with the aforementioned blood tests. Then, the accuracy of detecting these conditions increases to about 95% . That's a high percentage, right?

Are there any risks with this scan?

No. Nuchal translucency is a very low-risk test. It is just like a regular ultrasound scan. It will not harm you or your baby.

What happens if the NT scan results are abnormal?

This is where many mothers get scared. I would like to remind you again that the `NT` scan only indicates the risk of the baby having a certain condition. So, if your scan result is abnormal, meaning the `NT` value is high, don't panic .

Your doctor will then tell you about several diagnostic tests . These tests include:

• Chorionic Villus Sampling (CVS) : This involves taking a small piece of tissue from your placenta and testing it for genetic conditions. This is usually done between 10 and 13 weeks of pregnancy.
• Amniocentesis : This is done a little later in pregnancy, usually after 15 weeks. This involves using a needle to remove a small amount of amniotic fluid from your uterus. This fluid contains the baby's cells, and these cells can be tested to detect genetic abnormalities or infections.

It is from the results of these tests that we can accurately tell whether the baby has a certain condition or not .

Additionally, if the `NT` value is high, the doctor may also order a scan called a fetal echocardiogram to specifically look at the baby's heart, as an abnormal `NT` value can be associated with certain fetal heart defects.

Don't be afraid! The most important thing is...

Just because your NT scan results are abnormal doesn't mean your baby has a problem. Don't worry, don't panic . Your doctor will do more tests, or look for signs of another problem on your ultrasound or blood tests. They may refer you to a genetic counselor . That way, you can learn more about these conditions, their risks, and what other tests are available.

What is a normal NT value?

The amount of fluid behind the baby's neck increases slightly as pregnancy progresses. This means that the average value at 13 weeks may be slightly higher than the average value at 11 weeks.

Different medical institutions present slightly different NT thresholds for additional testing. These are based on the NT value as well as gestational age.

However, in most pregnancies, if the NT value is above 3 mm or 3.5 mm , it is recommended to discuss genetic counseling and additional testing. However, this is just a value, and your doctor will give you the best advice based on your situation.

Does an abnormal NT scan mean the baby has Down syndrome?

No, not at all . An abnormal nuchal translucency scan result does not mean that the baby will definitely have Down syndrome or another congenital condition. It only means that the baby is at increased risk or more likely to have such a condition.

Even if the NT value is normal, doctors may want to do blood tests in addition to the NT scan because this can give a more accurate assessment of your risk. In some cases, further prenatal testing is needed to determine the possibility of your baby being born with a genetic condition.

How long does it take to know the results?

In most cases, the doctor can tell you the results of the NT ultrasound scan on the same day . This means that the amount of fluid behind the neck can be measured and the value can be known on the same day.

However, the results of the blood tests done with the ``first-trimester screening'' can take a few days or a week or two to come back . Many doctors wait until all these results are in before they can calculate whether the baby is at risk or not. Only then will they explain the full picture to you.

Finally, take-home message

The ``Nuchal Translucency (NT)'' scan is an important initial test that helps determine the baby's risk of having a congenital or genetic condition.

• This is only a screening test , not a diagnostic test.
• Don't worry if the results are irregular. It just means that more testing is needed.
• There is still a chance that you will have a healthy baby .
• Talk to your doctor carefully about what your test results mean and what to do next.
• Talking to a genetic counselor and discussing the pros and cons of future testing will be very helpful.

I hope this information has helped you gain a better understanding of the NT scan. Never be afraid to ask your doctor any questions or concerns you may have.

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