Abnormal Nuchal Translucency Screening

If you find yourself in the position where you’re having to think about further prenatal testing following an abnormal scan or blood test result, I completely understand how your feeling. When you’re told a scan doesn’t look right or blood results are a cause for concern, you immediately think the worst. Until it’s explained to you in greater detail, you also have no idea what the problem could be, the possibilities are endless.
I was in this position not long ago and remember holding back the tears while waiting to be spoken to by a fetal medicine unit doctor as I’d just had an abnormal 12-week scan and had no idea what was wrong with my baby. The days following were spent googling like crazy and trying to cram as much information as possible into my brain in order for me to feel like I could be prepared for anything. Although, as you know, nothing you do can really prepare you for the news that something could be wrong with your unborn child. For this reason, I wanted to put my own version and thoughts on the Nuchal Translucency & testing out there for anyone who may find themselves in a similar place.

What is Nuchal Translucency & why could it be a cause for concern?

The Nuchal Translucency screening, or NT screening, is done between week 11 and 13 of pregnancy, usually during your 12-week scan. It is a specialised screening that helps doctors determine if statistically, the baby has an increased risk of having a chromosome abnormality, such as Down’s syndrome, Edwards syndrome, or Patau’s syndrome.

The nuchal fold is a clear space at the back of the baby’s neck and this is the area that checked during the scan. In baby’s with chromosome abnormalities, this space tends to accumulate fluid, making the area thicker than it would normally be. Therefore babies with increased fluid at the back of their neck are statistically at an increased risk of having a chromosome abnormality.
A baby who has a chromosome abnormality tends to have learning disabilities and mild to severe birth defects, caused by having an extra copy of a specific set of chromosomes.

This is a good time to point out that if your baby has an increased thickness at the back of the neck it does not automatically mean baby definitely has a chromosome abnormality. This is just an initial screening test at this stage and is not a diagnosis of any kind. It just means you could be at an increased risk. You will be offered a blood test which will take other factors into account – your age & certain hormone levels in your blood to assess your risk factor.

What is a normal NT reading?

Different hospital organisations vary slightly on what they consider a normal reading. For example, my own hospital considers anything under 3.5mm normal. However, after much research, it seems anything under 3mm is generally considered normal.

How reliable is a Nuchal Translucency screening

The nuchal translucency screening alone has quite a high margin for error. Therefore they are best paired with blood results which improve reliability, although are still only a risk factor and not a definitive answer.

The combined test which incorporates the NT screening with a blood test provides a risk factor based on the NT reading, blood hormones levels & your age.

What if my result is High Risk

Once you have had a combined test – NT scan & Blood test, you will receive a result that will show you are either high risk or low risk.

If your result comes back with anything less than 1 in 150 chance of having a baby with one of the 3 abnormalities, Down’s syndrome, Edwards syndrome, or Patau’s syndrome then this is considered high risk. Anything over 1 in 150 is considered low risk.

Should you receive a high-risk result the first thing to do is not panic. There are many women who have received a high-risk result and gone on to have perfectly healthy babies.

Your doctor will provide you with all the options available to you at this stage. There are 2 further tests that can be completed on the NHS which do give you a definitive answer on whether your baby has a chromosome abnormality and which one it is. A CVS (chorionic Villus Sampling) and Amniocentesis.

What is a CVS? 

A CVS is not routinely offered in pregnancy. It’s only offered if your baby is considered high risk for a chromosome condition.
You do not have to have a CVS if it’s offered. A CVS carries a very small risk of miscarriage therefore please ensure you are fully aware of what is involved in this test and what other options may be available to you.

How is a CVS performed? 

A CVS is usually carried out between weeks 11 and 14 of pregnancy.
A small sample of cells are removed from the placenta by either: inserting a needle through your tummy (the most common method) or a tube inserted through the cervix.

The test itself takes around 10 minutes and although can be uncomfortable, it is not considered painful.

What risks are involved with CVS? 

There is a risk of miscarriage and infections with this procedure. The chance of miscarriage following a CVS is around 2 in 100. Therefore, please ensure you are aware and have considered all of your options before having a CVS.

Results from a CVS

You would usually receive the first part of your result within 3 days, which will tell you if your baby had Down’s syndrome, Edwards syndrome, or Patau’s syndrome. If other, more rare conditions are being tested for, this may take a little longer, around 2 to 3 weeks for those results.

Unfortunately, there is no cure for chromosome abnormalities therefore you need to consider all your options very carefully. A specialist doctor will discuss all your options with you.

What is Amniocentesis?

An Amniocentesis is where a small sample of amniotic fluid is removed for testing. This test is usually carried out between weeks 15 & 20, although it can be performed later if necessary.

Unfortunately, this test also carries a risk of miscarriage so please consider all your options before proceeding.

How is Amniocentesis performed? 

An Amniocentesis is performed by inserting a long needle through your abdominal wall and into the amniotic sac that surrounds the baby. A small sample of amniotic fluid is removed for analysis, all while being guided by an ultrasound image.

The test itself takes around 10 minutes and although can be uncomfortable, it is not considered painful.

What risks are involved with Amniocentesis? 

There is a risk of miscarriage and infections with this procedure. The chance of miscarriage following amniocentesis is around 1 in 100. Therefore, please ensure you are aware and have considered all of your options before having this procedure.

As your pregnancy will be at a more advanced stage before you receive your results, you’ll have less time to consider your options following the result. 

Results from an Amniocentesis

You would usually receive the first part of your result within 3 days, which will tell you if your baby had Down’s syndrome, Edwards syndrome, or Patau’s syndrome. If other, more rare conditions are being tested for, they can take 3 or more weeks to receive the results. 

If you choose one of the two tests above, you will receive a definitive answer on whether your baby has a chromosome abnormality. Having a definitive answer to the question of your baby having a chromosome disorder helpful to have. Not only does it put your mind at ease if your result is negative but it also allows you to mentally prepare for what is to come should your result be positive.

If your result is positive, you will have some decisions to make when it comes to deciding whether to continue with the pregnancy. Please don’t try to make this decision alone. Speak with your partner, family, doctors, and make sure you have all of the information you can on the specific chromosome condition your baby has been diagnosed with. There are no right and wrong answers here. Your decision should be based on what is best for you and your family.

NIPT (Non-invasive prenatal testing)

Another test that is available but unfortunately is not currently available through the NHS, therefore, is something you will have to pay for yourself.

The test itself is called NIPT (Noninvasive Prenatal Testing). This is a test that is completed via taking some blood from mum and therefore carries no risk of miscarriage to baby.

This sounds like a great alternative to a CVS & Amniocentesis but unfortunately, this test can not give you a definitive answer on whether your baby has a chromosome abnormality or not.

How accurate is a NIPT?

What it does do is take a more in-depth look at the mother’s DNA in the bloodstream to identify if the baby is affected by certain chromosomal abnormalities. The test will only check for 3 chromosome disorders – Trisomy 21 (Down’s Syndrome, Trisomy 18 (Edwards syndrome) & Trisomy 13 (Patau’s syndrome) and is close to 99% accurate for Down’s syndrome and slightly less for the other two syndromes.

My own experience of this test

I have personal experience of this particular test as this is what we opted for rather than having one of the above more invasive tests. For us, the cost of this test was £315.00. It was a simple blood test completed by my hospital. Due to the current covid pandemic, my hospital asked me to post the blood sample myself special delivery so I could ensure it got to the lab it needed to in good time. They packaged the sample in a small parcel box with all the information and delivery address etc included. All I had to do was take it to a post office and pay for the 24hr special delivery.

If you would like to read more about why we needed a NIPT, take a look at my post Baby No. 2 Is On The Way

 

About Author

Hi, I'm Alex, welcome to my little corner of the internet.
I'm here to share my journey to motherhood and beyond. You may not find structured advice from a 'Stepford housewife' style mum, but you will get honesty & realism from a regular mum just like you.
From IVF, women's health & being a redhead, to pregnancy, toddlerhood & life as a work-from-home mum, I've got it all.
So stay and take a look around, you never know what you might find.

(5) Comments

  1. lynnmumbingmejia says:

    Very interesting read! I’m not as mummy yet and have not gone through it but I loved learning more about Abnormal Nuchal Translucency Screening. Thanks for sharing xx

    Lynn | http://www.lynnmumbingmejia.com

    1. One Clueless Mum says:

      Not something i thought i would have to learn about myself 😁
      Thank you for commenting.

  2. This isn’t something I’m familiar with as I don’t have kids but this was really informative and definitely something all expecting parents should think about x

  3. This was really informative! It’s such an awful situation trying to balance the accuracy against the chances of miscarriage and trying your best to be as informed as possible before the little one arrives. If you can afford it, the cost of the blood test sounds like nothing compared to some of the other risks. x

    1. One Clueless Mum says:

      Thank you! Absolutely, knowing the results, either way is more than worth the cost of the test. Thank you for reading x

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