What Is a Nuchal Translucency Scan?

If you are approaching the end of the first trimester, you may have heard the term nuchal translucency scan and wondered what it involves. It is one of the most important screening tools available in early pregnancy — and understanding what it measures and what the results mean can help you feel far more informed and prepared.

What Is a Nuchal Translucency Scan?

A nuchal translucency (NT) scan is an ultrasound measurement taken between 11 and 14 weeks of pregnancy. It measures the thickness of the fluid-filled space at the back of your baby’s neck — known as the nuchal translucency. All babies have some fluid in this area, but a larger-than-average measurement can indicate an increased risk of certain chromosomal conditions, most commonly Down’s syndrome (trisomy 21), Edwards’ syndrome (trisomy 18), and Patau’s syndrome (trisomy 13).

When Is the Nuchal Translucency Scan Done?

The NT measurement is taken as part of the combined first trimester screening test, alongside a blood test that measures two specific pregnancy hormones — PAPP-A and free beta-hCG. Together, these form the combined screening test, which is offered by the NHS at the 11 to 14 week dating scan. The NT measurement can only be taken within this window — after 14 weeks the fluid is naturally reabsorbed and can no longer be accurately measured.

What Does the NT Measurement Mean?

An NT measurement of less than 3.5mm is generally considered within the normal range, though what is considered normal varies with gestational age. The NT result is not used in isolation — it is combined with the blood test results and your age to calculate an overall risk score. This risk is expressed as a ratio, such as 1 in 500 or 1 in 150.

A result of 1 in 150 or higher is considered higher chance and will be offered further diagnostic testing. A result lower than 1 in 150 is considered lower chance. It is important to understand that this is a screening test, not a diagnostic test — a higher chance result does not mean your baby has a chromosomal condition, and a lower chance result does not guarantee they do not.

What Happens If the Result Is Higher Chance?

If your combined screening result comes back as higher chance, you will be offered further testing to get a definitive answer. Your options include:

• Non-invasive prenatal testing (NIPT) — a blood test that analyses fragments of your baby’s DNA in your bloodstream. Highly accurate and carries no risk to the pregnancy. Available privately if not offered on the NHS

• Chorionic villus sampling (CVS) — a small sample of placental tissue is taken for chromosomal analysis. Diagnostic and definitive, but carries a small risk of miscarriage

• Amniocentesis — a small sample of amniotic fluid is taken for chromosomal analysis. Also diagnostic and definitive, with a similar small risk of miscarriage

Is the NT Scan Compulsory?

No. The nuchal translucency scan and combined screening test are offered to all pregnant women in the UK but are entirely optional. Some parents choose not to screen, preferring not to know their risk score. Others feel strongly that they want as much information as possible. There is no right or wrong decision — it is entirely personal.

Early Pregnancy Scanning at MyBaby Ultrasound, Camberley

At MyBaby Ultrasound in Camberley, we offer private early pregnancy scans from 6 weeks, performed by experienced, CQC-registered sonographers. While the full combined screening test (including blood tests) is an NHS service, our early scans can confirm your pregnancy, detect a heartbeat, and provide detailed images of your baby ahead of your NHS dating scan appointment. Scans start from just £65 with no referral required.