The nuchal scan is an important part of your antenatal care that can reveal a lot about your baby’s health. The scan is named after the nuchal translucency test, which will be used to screen for certain kinds of abnormalities.
The Nuchal Translucency Test
The nuchal translucency test looks at an area called the nuchal fold
, which is visible during the ultrasound at the back of your baby’s neck. The fluid in this nuchal fold can be measured to determine if it is within the normal range. All babies have a certain amount of fluid in this area, but babies with certain chromosomal abnormalities are more likely to have a lot of it.
As well as measuring the nuchal fold, the sonographer will also check for the presence of the nasal bone during the scan. If the nasal bone isn’t visible at this point in development then it can indicate that your baby is more likely to have a chromosomal abnormality, especially if the nuchal fold measurement was also unusual.
You will also be given a blood test when you have the nuchal scan. The test will measure the levels of two different hormones in your blood, which can help us to estimate the risk. Unusual hormone levels can indicate that your baby is more likely to be affected.
The results from the scan and blood test will be combined with certain other factors, such as your age, in order to provide the most accurate result. The combined test can detect about 84% of babies with Down’s syndrome.
You will be given two results once all of this information has been analysed. The first result will tell you if your baby is at higher risk of Down’s syndrome. The second one will tell you if there is a higher risk of Edward’s or Patau’s syndrome. You won’t get these results right away as we’ll need to wait for the results of the blood test in order to provide the most reliable information. However, we should be able to provide your result on the same or next day.
What Are Chromosomal Abnormalities?
The nuchal translucency test is used to screen against certain kinds of chromosomal abnormality that can cause the nuchal fold to become thicker than usual. A chromosomal abnormality happens when there is an extra copy of one of the chromosomes in the baby’s cell. This can happen if there was a mistake when the egg or sperm cell was formed. The extra chromosome can have a dramatic effect on the baby’s development.
The three most common types of chromosomal abnormality can all be screened for during the nuchal scan:
- Down’s Syndrome: usually caused by an extra copy of chromosome 21, it can cause learning difficulties and a higher risk of certain health problems
- Edward’s Syndrome: caused by an extra copy of chromosome 18, it causes very serious health problems and is usually fatal before or shortly after the birth
- Patau’s Syndrome: caused by an extra copy of chromosome 13, it can also cause severe abnormalities and is usually fatal before or soon after birth
The nuchal translucency test isn’t perfect and it can’t diagnose any of these conditions for certain. However, when other factors such as the parent’s age are taken into account, it can tell us which babies are more likely to be affected.
Other Checks at the Nuchal Scan
Ultrasound scans can reveal a lot about your baby’s health and wellbeing
. In addition to the nuchal screening tests, we’ll also perform some extra checks during the nuchal ultrasound. We will:
- Measure your baby to see how well he or she is growing
- Check that everything is developing as expected
- Confirm the heartbeat
- Look for any structural abnormalities that might be visible at this stage
If you haven’t already had an ultrasound scan, then this scan will also be a chance for you to:
- Get a more accurate estimate of your due date
- Find out if you’re expecting twins or more
- See your baby for the first time
- Get your first baby pictures and videos
Having the Nuchal Scan
The nuchal scan is very similar to the other ultrasounds you will have during pregnancy. The only difference is that there is a stricter time limit for when you can have the scan. The nuchal translucency test can only be performed at a certain stage of your baby’s development, so you will need to arrange the scan between 11 weeks 5 days and 13 weeks 5 days.
When you have the nuchal scan, it will be performed in the same way as any other trans-abdominal ultrasound. You will be asked to lie down and remove any clothing that is covering your belly. The sonographer or consultant will put some gel on your skin. The ultrasound probe will then be passed across your belly in order to get pictures of your baby from different angles.
You will get the full results of your nuchal scan within a couple of days of the ultrasound and blood test. We will provide a complete report to add to your maternity notes as well as ultrasound pictures and videos for you. In most cases, there won’t be any signs of abnormalities. If any potential problems are detected, you will be able to discuss them with an experienced sonographer or consultant at the clinic. You’ll also get advice on your next steps, which might include NIPT (if you haven’t already had it) or an invasive test like amniocentesis to confirm the result.
It is your choice whether or not to have the nuchal translucency test. You will also be able to decide what you want to do with the information if you are given a higher risk result. Although it can be worrying to have any kind of medical test, in most cases the nuchal scan will simply provide reassurance that your baby is not at higher risk of abnormalities.
Are you worried about having the nuchal scan? Do you have any advice for other parents who are about to have this screening test?