What is Nuchal Translucency?

The term Nuchal Translucency is known as the name of the fluid collection beneath the skin behind the baby’s neck.

It is an ultrasound scan that measures the nuchal translucency of the baby.

What exactly is the NT scan procedure?

Nuchal translucency or an NT scan procedure is an ultrasound that measures the amount of fluid behind your baby’s neck in the first trimester of pregnancy.

This routine scan is important because it can help to assess your baby’s risk of certain chromosomal conditions, such as Down syndrome.

The nuchal translucency (NT) scan is performed between the 11th and 14th week of pregnancy.

The doctor would then assess the amount of fluid behind the fetus’s neck during this test. It is carried out within the first trimester of pregnancy.

It is used to help assess the risk of the baby having certain congenital conditions such as Down syndrome. When combined with other first-trimester screenings, it can be pretty accurate in detecting these conditions.

NT ultrasound is a screening test — it cannot diagnose a condition definitively. However, it can give your healthcare provider valuable information about whether or not further tests or monitoring may be needed.

What does a Nuchal Translucency test for?

An NT scan procedure looks at your baby’s nuchal translucency at the back of the neck for fluid accumulation. This area is called the nuchal fold.

All babies have some fluid present, but healthcare providers have found that more fluid tends to accumulate in babies with chromosomal or genetic conditions.

This increased fluid could indicate your baby has a condition like Down syndrome (trisomy 21), Patau syndrome (trisomy 13), or Edwards syndrome (trisomy 18). A higher NT measurement may also indicate an increased risk for congenital heart conditions. The results of the NT scan can help determine if your baby is likely or unlikely to have these conditions.

In addition to screening for chromosomal abnormalities, the NT scan also assesses your unborn baby’s anatomy for any structural abnormalities to some extent.

Other anomalies identified at the time of NT may increase the risk for genetic or structural conditions. However, many of these conditions can be managed successfully with early detection and proper prenatal care.

Why would my doctor refer me to have this scan?

Nuchal translucency or an NT scan procedure is a routine prenatal screening that can help identify potential health risks for a developing baby.

This test is usually recommended for all expectant mothers. Your referring doctor will be able to tell you if you are eligible for a Medicare rebate.

Your doctor will likely recommend a nuchal translucency scan in order to

  1. Confirm the exact date of the pregnancy and due date.
  2. Determine if the pregnancy is single or multiple.
  3. Assess if the fetus is growing appropriately and appears to be developing normally.
  4. The scan is strongly recommended for women who are over 35 years of age as there is increased risk based on the age of the mother.
  5. If there is a prior history of pregnancy with a fetal abnormality or if there are genetic conditions in the family, this scan can provide valuable information.

When is a Nuchal Translucency scan done?

Your healthcare provider will usually perform an NT scan during your baby’s 11th-13th week of gestation, or when your baby is between 45-84 millimeters from crown to rump.

This is because, after 14 weeks of gestation, the fluid behind your baby’s neck begins to get reabsorbed by the body, making it harder to measure later on in pregnancy. NT tests are often done as part of a first-trimester screening test.

How do I prepare for a Nuchal Translucency scan?

To get an accurate assessment, it’s important that you follow some simple guidelines.

  • First, drink some water before the test. This will help create clear ultrasound images of your abdominal area. You don’t want to be uncomfortably full, just enough so that the inside of your abdomen can be seen clearly. The radiology facility where you have the scan will give you specific instructions on how much fluid to drink beforehand.
  • Second, wear comfortable clothing that gives easy access to your lower abdomen—the area where the ultrasound probe will be placed.

What is the procedure?

  • To prepare for the NT scan, the mother may be asked to drink plenty of fluids so that her bladder is full. Although it is not mandatory. This helps to obtain clear images of the baby during the scan.
  • Once her bladder is full, she will be asked to lie on her back or side on an examination table.
  • A gel will be applied to her abdomen, and a transducer device (a handheld device that emits ultrasound waves) will be pressed against the gel.
  • The transducer captures images, which are then displayed on a monitor.
  • The technologist performing the scan will measure the thickness of fluid collected at the back of the baby’s neck.

During the scan, a transducer (wand) is used to take measurements of the baby from the crown to the rump. The sonographer will also measure the thickness of the nuchal fold.

These measurements, along with your age and the baby’s gestational age, are used to calculate the risk of chromosomal abnormalities.

The  NT scan usually takes around 30 minutes. However, sometimes the sonographer may ask you to wait in the room after the scan so they can check the images with a radiologist or specialist. If more scans are needed, or if the specialist needs to look at the images on screen, this may add some time to your appointment.

What are the risks of a Nuchal Translucency scan?

Abdominal ultrasounds are a routine and safe part of prenatal care. They use sound waves to create images of the developing baby and do not involve exposure to radiation. Multiple scans can be performed without any increased risk.

Transvaginal ultrasounds are also safe and pose no risk of miscarriage. This type of ultrasound is used when the pregnancy is at an early stage or if the doctor needs a more clear view of the baby.

What are the benefits of a Nuchal Translucency scan?

The main purpose of  NT screening is to evaluate the likelihood of Down syndrome or other fetal conditions as early as possible during pregnancy. This way, you can discuss the results with your doctor and make a decision about whether or not to continue with the pregnancy.

If screening does identify a possible risk, additional tests may be needed to confirm the results before making a final decision (such as amniocentesis or chorionic villus sampling).

How are NT scan results calculated?

The likelihood of your baby having a chromosomal abnormality is linked to several factors, including the thickness of the nuchal translucency, your age, and the gestational age of your baby.

Your age is a significant factor because although anyone can have a baby with a chromosomal abnormality, the risk increases as you age.

The thickness of the nuchal translucency can give important clues about whether or not a baby has certain abnormalities. In general, the thicker the nuchal translucency at a given gestational age, the higher the chance that the baby will have an abnormality.

However, your healthcare provider might recommend taking a blood test (a double marker test) as it provides a more accurate result than an NT scan.

What does NT scan results mean?

It’s important to discuss the meaning of your genetic test results with a healthcare professional or genetic counselor. The results can be difficult to interpret on your own, and they may have implications for your health and the health of your family. Many genetic testing centers will provide both individual lab results and a final calculated result using a special formula.

The results of your baby’s chromosomal screening will be given as a ratio. This ratio expresses the likelihood of your baby having a chromosomal defect.

For example, a risk of 1 in 100 means that out of every 100 women with this result, one baby will have Down syndrome and 99 will not. A risk of 1 in 1,200 means that for every 1,200 women with this result, one baby will have it and 1,199 will not. The higher the second number is, the lower the risk is.

When you get your results back from a screening test, your provider will tell you if they are “normal” or “abnormal.” This is based on a cutoff point that indicates the risk of there being a problem. For example, some tests use a cutoff of 1 in 250.

This means that if your results show a 1 in 1,200 chance of there being a problem, it would be considered normal because the risk is lower than 1 in 250. However, if your results show a 1 in 100 chance of there being a problem, it would be considered abnormal because that risk is higher than the cutoff point.

Remember that even if you get a normal screening result (screen negative), this isn’t a guarantee that your baby has no chromosomal defects. And if you get an abnormal screening result (screen positive), this doesn’t mean for sure that your baby does have chromosomal defects – just that they are more likely to have them.

In most cases, babies who test screen positive do not actually have any chromosomal problems – only about one-third of babies who have increased nuchal translucency measurements turn out to have chromosomal defects.

How effective is Nuchal Translucency testing?

That means that the test correctly identifies 30 percent of babies with Down syndrome or other chromosome disorders. However, when NT screening is combined with other tests in the first trimester, such as measurements of the hormone PAPP-A and the quad screen, the accuracy rate increases to between 94 and 96 percent.

NIPT is even more accurate than NT screening, with a 99 percent detection rate for Down syndrome. Therefore, combining NT results with NIPT can give parents a very good idea of whether or not their child has a chromosomal disorder.

The Takeaway

An NT scan is a simple, safe way to get information about your baby’s health without causing any harm. This test is recommended during the first trimester, but it’s ultimately up to you whether or not you want to have it done.

Some women choose not to have the test because they don’t want to know their risk, but if you’re feeling anxious or worried about the results, talk to your doctor.

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