Nuchal translucency scan

A nuchal translucency scan (NT scan) is an ultrasound scan done in early pregnancy. It is part of the combined first trimester screening test, which may also include a blood test. 

The scan measures a small fluid-filled space behind your baby’s neck. This helps your doctor and midwife estimate the chance of your baby having a chromosomal difference. 

It is sometimes called an early structural ultrasound.

An NT scan is usually done between 11 weeks and 13 weeks and 6 days of pregnancy. The scan is offered to everyone and is optional. 

An NT scan can find early signs of:

• Down syndrome
• heart differences
• other chromosomal or structural differences

It can also help screen for pre-eclampsia, a pregnancy complication that affects blood pressure and the placenta.

The NT scan is a screening test, not a diagnosis. Results are usually reported as ‘low risk’ or ‘high risk’.

• A ‘low risk’ result means it is less likely that there is a difference present. 
• A ‘high risk’ result means it is more likely that there is a difference present. 

If the fluid-filled space behind your baby’s neck is larger than expected, your doctor or midwife may suggest more tests or scans.

Ultrasound scans are safe and do not harm you or your baby.

Ultrasound has been used safely in pregnancy for many years. Australian expert groups, such as the Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) and the Australasian Society for Ultrasound in Medicine (ASUM), say there is no evidence that routine pregnancy ultrasound harms you or your baby when it is done by trained staff and used only when needed.

An NT scan is usually done by a trained professional called a sonographer. The scan is performed in a radiology clinic, a specialist clinic or a hospital.

An NT scan is done using a handheld ultrasound wand. The wand may be placed on your tummy or inside your vagina, depending on:

• how far along your pregnancy is
• your baby’s position
• your body shape

Your sonographer will

• measure your baby’s length to make sure the scan is done at the right time 
• check if your baby is lying on their side with their neck in a relaxed position
• measure the fluid-filled space behind your baby’s neck — they will zoom in to the picture on the screen 

The scan usually takes around 20 minutes. If your baby is moving around a lot, it may take longer.

How should I prepare for a nuchal translucency scan?

Before your scan, think about why you want to have it and how you might feel about the results. 

Talk with your partner, a friend, family member, your doctor or midwife so you can make an informed choice. 

Here are some tips to help you prepare:

• Wear loose, comfortable clothes so your tummy can be easily accessed.
• Ask if you need to have a full bladder before the scan. Read more about what to ask your doctor about tests and scans.
• If you are having combined first trimester screening, you will also need a blood test.

An NT scan is safe but like any test, it can sometimes cause worries or lead to more tests. For example:

• If the fluid behind your baby’s neck is thicker than usual, your doctor or midwife may suggest more tests. This may feel worrying.
• The scan might find something that needs checking or follow-up. This may be upsetting or unexpected.
• Sometimes, the first scan does not show everything clearly, so you might need to come back for another one or have the scan done as a vaginal ultrasound.

Your doctor or midwife can help you understand the results and what to do next.

Non-invasive prenatal testing (NIPT), also known as cell-free DNA testing (cfDNA), is another screening option for chromosomal abnormalities.

It is more accurate than an NT scan or combined first trimester screening. NIPT is not currently funded by Medicare and can be expensive.

Talk with your doctor or midwife for advice about which antenatal screening tests are right for you.

• Your doctor, obstetrician or midwife can answer your questions and help you understand your screening options.
• The Royal Women’s Hospital has information on genetic testing in pregnancy.
• A genetic counsellor can help guide you through the meaning of your results and any decisions you may need to make. Ask your doctor to refer you to one.
• Genetic Counselling Australia offers advice and support for families.
• The Human Genetics Society of Australasia can help you find a genetic counsellor in your area.