What is a nuchal translucency scan?

A nuchal translucency scan is an ultrasound scan that measures your baby’s nuchal translucency — a fluid-filled space behind your baby’s neck. This measurement can help your doctor estimate the risk of your baby having a chromosomal abnormality such as Down syndrome.

Should I have a nuchal translucency scan?

The chances of having a baby with a chromosomal abnormality are greater the older you are when you get pregnant. However, anyone can have a baby with chromosomal abnormalities, so screening is offered to everyone, but the decision to have the scan is yours.

While scans can reassure you that your baby is developing normally, you may also learn that your baby has an abnormality. For this reason, before you have the test it’s a good idea to think about why you are choosing to do it, and what you would do next if your screening test showed you were at a high risk of your baby having a chromosomal abnormality.

Some women choose not to have any tests or decide to have a diagnostic test instead (such as chorionic villus sampling or amniocentesis), which can give them more definite information about their baby’s health.

When is a nuchal translucency scan done?

A nuchal translucency scan is done between 11 and 14 weeks of pregnancy. If your doctor has referred you for a dating scan, it can often happen at the same time.

Who performs a nuchal translucency scan?

A nuchal translucency scan is usually performed by a specially-trained technician called a sonographer, but other health professionals, such as doctors or midwives with the relevant training, may also do it. The scan may be performed in a radiology clinic or a hospital.

How is a nuchal translucency scan done?

In early pregnancy, ultrasounds such as the nuchal translucency scan can be done through your abdomen or vagina. Your sonographer will choose a method based on several considerations, including how far along your pregnancy is and your body shape.

If your scan is done along your abdomen — transabdominally — you will be asked to drink a few cups of water before you arrive so that your bladder is full. This makes it easier to see inside your uterus (womb). The sonographer will apply some gel and gently move the ultrasound probe across your abdomen. It doesn’t usually hurt.

If your scan is done transvaginally, a small, lubricated ultrasound probe is gently inserted into your vagina. The probe may be a little uncomfortable but usually isn’t painful. Scans done this way can give more detailed pictures because the probe is closer to your uterus.

Ultrasounds do not harm you or your baby or increase your risk of miscarriage.

What do the results mean?

This is a screening test, so the results can’t tell you for sure whether your baby has a chromosomal abnormality. If your test returns a high-risk result, you may decide to have a diagnostic procedure such as chorionic villus sampling or amniocentesis, which can give you a definitive result.

Results are usually reported as ‘low risk’ or ‘high risk’. Low risk is fewer than 1 in 300 tests would indicate risk of chromosomal abnormality (for example, 1 in 450 tests); high risk is greater than 1 in 300 would indicate risk of abnormality (for example, 1 in 150 tests).

Your nuchal translucency scan results can be combined with a blood test, usually done in weeks 10 to 12 of pregnancy, to form a ‘combined first-trimester screen’, or CFTS. The combination of blood test and ultrasound results can give a more accurate estimate of your risk.

During the test, the sonographer may also:

• confirm that your pregnancy is in the right place and is not ectopic
• look for your baby’s heartbeat
• check if you are carrying more than one baby

Is there a cost for a nuchal translucency scan?

Medicare will cover your nuchal translucency scans, but you may have to pay out-of-pocket costs depending on where you go for the test. Ask about any fees when you book your appointment.

What are the alternatives?

Non-invasive prenatal testing (NIPT), also known as cell-free DNA testing (cfDNA), is another antenatal screening test for chromosomal abnormalities. It is more accurate than a nuchal translucency scan or the CFTS but is not currently funded by Medicare and it can be expensive. Some women choose to do NIPT instead of the CFTS, or after they get a high-risk result.

If you’re considering different options for antenatal screening, talk with your doctor or midwife for advice.

More information

Your GP, obstetrician or midwife can answer your questions and give you more information on antenatal screening tests. They may also refer you to a genetic counsellor to help guide you through the consequences of your results and any decisions you may need to make.