What is an NT scan? A guide to the 11–14 week scan

Medically written by Dr. Sushma Dhakal, MBBS · MD (Obstetrics & Gynaecology) · Fellowship in Fetal Medicine · Updated 30 October 2026 · 3 min read

The NT scan, also called the nuchal translucency scan or the 11–14 week scan, is one of the most useful scans in early pregnancy. It is a detailed ultrasound that checks your baby's early development and, together with a blood test, estimates the chance of certain chromosomal conditions such as Down syndrome.

When is the NT scan done?

The scan is done between 11 weeks and 13 weeks 6 days of pregnancy, when the baby's crown–rump length (CRL) measures 45–84 mm. Outside this window the measurement is no longer reliable, so it is important to book on time. If you are unsure of your dates, an early dating scan helps plan it.

What does the scan check?

Nuchal translucency: a small fluid space under the skin at the back of the baby's neck. All babies have some fluid; a thicker measurement is linked to a higher chance of chromosomal conditions and some heart problems.
Dating and number of babies: confirms how many weeks pregnant you are and, in twins, whether they share a placenta (chorionicity), which is very important for planning care.
Early anatomy: the skull, brain, spine, stomach, bladder, limbs and heart can already be seen. Some major problems can be detected this early.
Extra markers: the nasal bone, blood flow through the ductus venosus and the tricuspid valve can refine the risk.
Pre-eclampsia screening: blood flow in the uterine arteries plus your blood pressure can identify women who benefit from low-dose aspirin.

Combined screening: scan plus blood test

The NT measurement is combined with your age and a blood test (free β-hCG and PAPP-A). This combined test detects about 90% of babies with Down syndrome (trisomy 21). It gives a risk, such as 1 in 5,000 or 1 in 50. It does not give a diagnosis.

What if the result is "high risk"?

A high-risk result means the chance is higher than usual. Most babies with a high-risk result are healthy. Your options will be explained calmly in counselling:

NIPT (cell-free DNA blood test): a very accurate screening test with no risk to the pregnancy.
CVS or amniocentesis: diagnostic tests that give a definite answer about the chromosomes.
A detailed follow-up scan, including a fetal heart (echo) scan if the NT is increased.

Is the scan safe? How is it done?

Yes. Ultrasound uses sound waves, not radiation. The scan is usually done through the abdomen; occasionally a vaginal scan gives a clearer view. It takes about 20–40 minutes, and sometimes the baby needs to move into the right position. You do not usually need a full bladder.

Why choose an FMF-certified specialist?

NT measurement is very precise work: a fraction of a millimetre changes the risk. The Fetal Medicine Foundation (FMF, UK) certifies doctors who meet strict standards and audits them every year. Dr. Sushma Dhakal holds FMF certification for the NT scan.

Have questions about your pregnancy?

Book a consultation with Dr. Sushma Dhakal, Fellowship-trained fetal medicine specialist (FMF UK certified).

Book this scan Request Counselling

Frequently asked questions

When should I have the NT scan?

Between 11 weeks and 13 weeks 6 days of pregnancy (baby's CRL 45–84 mm).

Does the NT scan diagnose Down syndrome?

No. It is a screening test that gives a risk. Only CVS or amniocentesis can confirm a diagnosis.

Do I need a full bladder?

Usually not. Most NT scans are done through the abdomen without a full bladder.

Is the NT scan safe for my baby?

Yes. Ultrasound uses sound waves, not radiation, and is safe in pregnancy.

This guide is for general information only and is not a substitute for personal medical advice. Every pregnancy is different. Please consult your doctor about your own situation. In an emergency, go to the nearest hospital.