Nuchal translucency screening

Nuchal translucency scans are combined with a blood test and a mothers age to screen for chromosomal conditions. This is known as the combined screening test and is offered to all pregnant women in the NHS, usually during their dating scan.

What is the Nuchal translucency screening?

It’s anultrasound scan that measures the clear (translucent) space in the tissue at the back of the baby’s neck, known as the nuchal fold.

Research has established that fluid retention in the nuchal fold during the 11 to 13 week and six day's window may be a marker for Down’s syndrome and other chromosomal conditions.

It is important to remember that many babies who have more fluid than usual at the back of the neck at an early scan are born healthy and well.

Who should get a nuchal translucency screening?

All pregnant women are offered the NT scan as part of the combined screening test. The NT scan part of the screening is done as an ultrasound scan during week 11 and 14 of their pregnancy.

Where do I have the nuchal translucency screening?

The scan is carried out at most NHS antenatal clinics and is usually offered and done during the 12 week dating scan.

What happens if the sonographer can’t measure the nuchal translucency screening?

If baby is in a difficult position and the monographer can’t obtain an accurate nuchal translucent measurement, then you will not be able to have the combined screening test and will be offered the quadruple test instead. (Link)

Is there any risk from the test to my baby?

No, nuchal translucency screening does not pose any risk to your baby. 

How accurate is the nuchal scan?

The NT scan forms part of the combined test which combines the mother’s age and other factors includingblood test markers to predict the overall chance of the baby having one of the chromosomal conditions.

The combined test is not 100% accurate and identifies about 84-90 in every 100 babies affected by Down`s syndrome, Edward’s syndrome or Patau`s syndrome. It is more accurate than the quadruple test.

When do I get the results?

While the scan will only take a few minutes for the measurements of the nuchal fold to be made, the results are combined with your age and blood test measurements, so you may have to wait up to 2 weeks to get the results. You will usually get the results by letter. If there is a high risk result you will be offered an appointment to discuss the results and understand what they mean.

How to interpret the results from Nuchal translucency screening

As the combined test is just a screening test and not a diagnostic test, your combined test results won’t tell you for certain if your baby does or doesn’t have a chromosomal condition. Instead they will give you the chance—either higher chance or lower chance—that you might be carrying a baby with this condition.

You will get your results as a set of numbers that use a cut-off point of 150 for a higher chance result.

• Higher chance: if your result is 1 in 150 or 1 out of a number less than 150 (e.g. 1 in 100) then your baby has a higher chance of having Down’s syndrome.
• Lower chance: if your result is more than the cut-off value of 150 (e.g. 1 in 200) then your baby has a lower chance of having Down’s syndrome.

Out of 100 screening results, more than 95 will be lower chance and fewer than 5 will be higher chance. A lower chance result doesn't guarantee that your baby won't have Down’s syndrome. Likewise, a higher chance result doesn't guarantee that your baby will be born with the condition.

My combined test results are high risk, what are my options?

If your result is higher chance, you’ll have 3 options.

• You can be offered a diagnostic test, such as amniocentesis (needs linking) or chronic villus sampling (CVS). This can diagnose whether baby has a chromosomal condition but comes with a miscarriage risk of 1%.
• You can be offered a more accurate screening test called a Non-Invasive Prenatal Testing (NIPT). This is a more accurate screening test and can detect 99% of babies with down syndrome. It won’t give you a diagnosis but it carries no risks. You’ll still be offered a diagnostic test to confirm things if your NIPT result is positive.
• You can have no further testing.