Nuchal scan

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What is the nuchal scan?

The nuchal scan is a screening test taken between 11 + 2 and 14 + 1 weeks of your pregnancy to aid in the assessment of Down’s, Edwards’ and Patau’s syndrome. It is also known as the combined screening test.

This screening test can tell you what the chances are of your baby having any of these three conditions. It will not tell you if they definitely have the condition.

For more detailed information, you can access the Fetal Anomaly Screening Programme (FASP) information at:

Down’s syndrome, Edwards’ syndrome and Patau’s syndrome: GOV.UK

This scan usually takes around 20 minutes.

What happens before my examination?

Please attend with a full bladder for this examination. Usually drinking a pint of water 1 hour before the scan and not emptying your bladder is sufficient.

Please note we are a university trust and regularly have trainee sonographer and student midwives present at the scan. If you do not wish for a student to be present please inform the sonographer.

What will happen during the examination?

• The sonographer will perform two measurements.

• Crown rump length (CRL). This measures the length of your baby from head to bottom and is used to calculate estimated date of delivery (EDD). Using the ultrasound measurement is proven to be more accurate that using the period date in working out how many weeks pregnant you are.

• Nuchal translucency (NT). This is the measurement behind the neck of your baby. This measurement is used with your blood test to calculate the risk of Down’s, Edwards’ and Patau’s Syndrome. You can request to screen for all three, just Down’s or just Edwards’ and Patau’s.

The scan will also perform a basic check on your baby’s anatomy including the head and brain, abdomen, arms and legs. Any concerns will be referred to the screening team.

If your baby is not in a very easy position for the sonographer to see, you may be asked to wriggle your hips, jump up and down or walk around outside.

The NT measurement is not always possible to measure. If, after two attempts on the same day, this is not possible a Quad test will be explained and offered to you.

What happens after?

The sonographer will explain the results and a copy will be given to you. If there have been any abnormalities identified you will be referred to a screening midwife for support and further information. You may be required to see a fetal medicine consultant for confirmation or second opinion. If you do not understand the results please ask the sonographer to explain. We will book your 20 week scan appointment after your scan is completed.