What is the NT (nuchal translucency) scan?
In short
- The NT scan checks the fluid at the back of your baby's neck, using ultrasound.
- NT stands for nuchal translucency — that fluid space.
- It's done at 11 to 14 weeks, often with a blood test on the same visit.
- A thicker result means a higher chance, not a diagnosis; your doctor will explain what's next.
What happens
- A sonographer scans your abdomen (or uses an internal probe if needed) and measures the fluid space at the back of your baby's neck.
- This is usually combined with a blood test taken from your arm around the same time — together these make up the "combined test".
- Your result is given as a chance (for example, 1 in 500), not a yes/no answer.
Baby's sex is never revealed
It is illegal in India for anyone -- including your sonographer -- to reveal, or help you find out, the sex of your baby before birth. This is the Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994.
Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994. Read the Act (India Code).
The details: numbers and where they differ
In the source's own words
The first screening test for Down's syndrome, Edwards' syndrome and Patau's syndrome is called the combined test. There are 2 parts to the combined test: a blood test when you're between 10 and 14 weeks pregnant, with blood taken from your arm; an ultrasound to measure the fluid at the back of your baby's neck during your 12-week scan (dating scan), when you're between 11 and 14 weeks pregnant.
NHS (UK), Screening for Down's syndrome, Edwards' syndrome and Patau's syndrome. Quoted verbatim.
The numbers
| Measure | Value | Source |
|---|---|---|
| NT / combined first-trimester screening window (pregnant women) | 11–14 (NHS) / 10–13 (ACOG) weeks gestation | NHS (UK) |
Where sources disagree
exact week range for the NT/combined window
Sources differ here — shown side by side, not blended into one number.
NHS (UK)
The ultrasound part of the combined test is done during the 11-to-14-week dating scan, alongside a blood test taken from 10 weeks.
ACOG (US)
Both first-trimester tests (the blood test and the NT ultrasound) are usually done together between 10 and 13 weeks.
When to call your doctor
- If you're not sure whether you've been offered this scan, or when it's scheduled.
- If your result comes back as higher chance and you want to understand your options for further testing.
Discuss your results with your doctor: this page reports what these sources say, not advice for your situation.
Sources
- NHS (UK), Screening for Down's syndrome, Edwards' syndrome and Patau's syndrome. Quoted verbatim. OGL-style NHS content, free reuse with attribution.
- American College of Obstetricians and Gynecologists (ACOG), Prenatal Genetic Screening Tests (Patient FAQ). Named as the guideline this section describes; its text and tables are not reproduced here (All rights reserved (cite only)). Describes the NT ultrasound and a blood test as usually done together between 10 and 13 weeks, and says an abnormal NT measurement means an increased chance of Down syndrome or another chromosome difference.
Sources checked 2026-09-26. How we source and check every page.
Educational summary of named sources, not medical advice.