Nuchal Translucency Ultrasound: What You Need to Know

The nuchal translucency ultrasound might sound a bit sci-fi, but there’s nothing alien about it.

The nuchal translucency scan is a routine prenatal assessment helps your doctor determine the risk of your baby developing a chromosomal difference.

Whether you’ve announced it or not, you’re pregnant and things are about to get real, mama.

For the next nine months, your (and your baby’s) health will be monitored closely — and this will involve a few prenatal screenings, scans, and tests.

One such screening is the nuchal translucency ultrasound, which sounds a little scary and can be a bit of a mouthful.

But don’t worry, the NT scan is a perfectly safe, routine assessment — and here we explain the whats, whens, whos, and whys involved.

In this article: 📝

What is the nuchal translucency ultrasound?

So just what is nuchal translucency? [1]

Well, the NT ultrasound is focused on the small, clear (translucent) tissue at the back of your developing baby’s neck.

This is called the nuchal fold. [2]

The higher the nuchal fold measurement during the test, the higher the potential risk of chromosomal disorders being present.

What does nuchal translucency test for?

The nuchal translucency ultrasound offers an early indication of potential chromosomal issues, including Down’s syndrome, Patau syndrome, and Edwards’ syndrome, and can also be an early indicator of pregnancy loss. [3]

However, it’s important to note that an NT scan can’t actually diagnose anything at this stage.

Instead, the nuchal translucency test is used as a “soft marker” as babies with an increased level of fluid or a clear space at the back of the neck are statistically more likely to develop these syndromes.

Any high measurements at an NT ultrasound will often prompt additional tests (like amniocentesis) to figure out what’s going on.

Also, a recent study showed that nuchal translucency can help determine the survival rate of twins and triplets, so it could be useful for 'predicting' other things in pregnancy, too. [4]

How accurate is an NT ultrasound?

The nuchal translucency scan is not 100% conclusive.

When performed on its own, an NT ultrasound is only around 70% accurate — and false positives are relatively common. [5]

But if it is accurate, either way, this test gives you more time and headspace to prepare for your child’s needs.

To improve overall accuracy, your doctor will probably suggest pairing the NT ultrasound with non-invasive prenatal testing (NIPT), which is a type of blood test.

How accurate is 12-week scan for Down's syndrome?

The 12-week scan for Down’s syndrome is usually the nuchal translucency ultrasound.

However, at the same time, your doctor might look at other markers to see how baby’s developing, or if they’re showing any other signs of Down’s syndrome.

Some of these other signs of Down’s syndrome might be a flatter facial profile and listening to baby’s heart to hear how it flows. [6]

While the NT scan has a 70% accuracy rate, if your doctor identifies any of these other markers, that could increase the accuracy to 95%.

What happens at nuchal translucency scan?

The noninvasive nuchal translucency test involves an ultrasound wand on your abdomen (and ice-cold belly gel, obvs).

The sonographer will then pinpoint where baby’s nuchal fold is, then measure how thick it is on the ultrasound screen.

What blood test is done with NT scan?

During your nuchal translucency test, which could also be your first-trimester ultrasound, your doctor may also do a blood test.

This blood test checks your levels of hCG (human chorionic gonadotropin) and the succinctly-named pregnancy-associated plasma protein-A (PAPP-A). [7]

Your hCG levels will steadily rise during pregnancy, whereas your PAPP-A levels will continue to rise throughout the pregnancy ‒ signs both you and baby are healthy and strong. [8]

When should a nuchal translucency be done?

The NT scan usually takes place between week 10 and week 13 of pregnancy.

Any later than that and the tissue becomes too thick and is no longer clear, making the test results inconclusive.

What is normal nuchal translucency measurement?

Typically, a “normal” nuchal translucency measurement is less than 3.5mm when baby is between 45-84mm. [9[

From around 14 weeks, their nuchal fold grows quickly, so it’s harder to get an accurate nuchal fold measurement.

It’s also worth noting that the words “normal” and “abnormal” don’t genuinely describe a nuchal translucency fold measurement.

While they are scientific terms, they can be harmful words to use when describing babies’ development.

After all, every baby is beautiful, powerful, and strong, in their own way.

We’ll use the word “normal” in this guide, however, as it’s a commonly used term for mamas who are looking for answers.

Is 1.5 mm nuchal translucency normal?

Yes, a nuchal fold measurement of 1.5mm would be considered within the “normal” range.

What is the normal range of NT at 13 weeks?

A “normal” result at 13 weeks is 1.6-2.4 mm, while the average nuchal translucency measurement is around 2.18 mm. [10]

What is abnormal nuchal translucency?

An “abnormal” nuchal translucency would be classed as anything measuring higher than 3.5 mm on the ultrasound screen.

However, a high nuchal translucency is not the only indicator of a chromosomal difference.

“Abnormal” nuchal translucency, “normal” baby (that is, a higher nuchal fold measurement and a baby without chromosomal differences) has been known to happen.

In fact, according to this study in 2011, the chances of having a baby with a high nuchal translucency but no major chromosomal differences ranges from “70% for NT of 3.5-4.4 mm, 50% for NT of 4.5-5.4 mm, 30% for NT of 5.5-6.4 mm, and 15% for NT of 6.5 or more.”.

It's important to remember that nuchal translucency can indicate markers of abnormalities, but not give you a diagnosis.

What happens if nuchal translucency is high?

If your baby has a high nuchal translucency, your doctor will likely suggest you have an additional test ‒ at this stage, it’s only a 70% chance that an “abnormal” nuchal translucency is an indicator of a chromosomal difference.

They might also suggest a fetal heart scan, because cardiac abnormalities can be associated with some chromosomal diagnoses.

It can be hard, but try not to worry yourself if baby does have a high nuchal translucency measurement ‒ it doesn’t always mean they will have a chromosomal difference.

Does a high nuchal translucency always mean Down syndrome?

Not necessarily. There can be lots of reasons for a high nuchal translucency measurement.

Some increased nuchal translucency causes include:

• Parvovirus, an infection that can increase baby’s nuchal fold measurement.
• Congenital heart defects (ranging from minor to major).
• Rare genetic syndromes
• Venous congestion ‒ high blood pressure

Can nuchal translucency decrease?

Yes, typically after about 14 weeks, the nuchal translucency tends to disappear ‒ the fluid becomes less clear.

Can nuchal translucency be too low?

Not likely ‒ the nuchal translucency measurement doesn’t have a minimum amount.

Some babies’ nuchal translucency measures in at 0.4mm, and they are classed as “normal” results.

Can you tell gender at nuchal translucency?

How can you tell boy or girl from NT scan?

Well, it’s actually quite common to find out baby’s sex during your 12-week nuchal translucency ultrasound.

It can pre fairly accurate, 80-95%, so if you’re keen to find out if you’re having a girl or a boy, this could be the right time! [11]

Is a nuchal translucency scan necessary?

The decision to do the NT ultrasound is entirely up to you. So, should you do it?

Well, the best thing about any sort of prenatal testing, including the NT test, is that it can help put your mind at ease.

Worrying about the health of your unborn baby is a common source of anxiety, and hearing that baby is developing well can be a real weight off your shoulders.

Should I worry about nuchal translucency screening?

No, there’s nothing to worry about during your nuchal translucency ultrasound.

There are no risks associated with an NT scan.

It’s quick, painless, and poses no danger to you or your baby.

It’s ultimately your decision whether you want to go for it.

Can nuchal translucency be wrong?

Yes, a nuchal translucency measurement can be wrong ‒ a high nuchal translucency doesn’t always mean baby has any chromosomal differences, or that there’s a chance of pregnancy loss.

It’s all about statistics.

Generally speaking, most babies with a known high nuchal translucency measurement are found later in pregnancy to have chromosomal differences.

There is also a chance that the actual nuchal translucency measurement itself is wrong ‒ there’s always the chance of human error.

Ultimately, the choice to do a nuchal translucency ultrasound is all yours, mama.

The best thing to do is talk it over with your doctor — and remember, the mamas on Peanut have your back, too.