What is the NT scan?
The NT scan — short for nuchal translucency scan — is a specialised ultrasound performed in the first trimester of pregnancy, typically between 11 weeks and 13 weeks 6 days. It is part of routine first trimester screening and is one of the most time-sensitive scans in pregnancy: the measurement window is narrow, so booking promptly once your obstetrician advises it is important.
The scan looks at the fluid-filled space at the back of the baby's neck. It also checks early anatomy, confirms the heartbeat, reviews the baby's position and movement, and can assess the nasal bone in some cases. Done within the correct window and by an experienced radiologist, it forms a vital first picture of how the pregnancy is progressing.
What does nuchal translucency measure?
Nuchal translucency refers to the fluid-filled space at the back of the baby's neck. All babies have some fluid here in the first trimester — a small measurement is entirely normal. What the scan assesses is whether this space is larger than expected for the gestational age.
An increased nuchal translucency can be associated with a higher chance of certain chromosomal conditions (such as Down syndrome, Edwards syndrome, or Patau syndrome), as well as some heart conditions and other structural differences. The measurement alone does not give a diagnosis — it contributes to a risk calculation that is interpreted alongside other factors.
What a normal NT looks like
- Generally below 3.5 mm, though the threshold varies slightly by gestational age
- Most babies have a normal NT measurement
- A normal NT is reassuring but does not rule out all chromosomal conditions
What a raised NT means
- A measurement above the expected range for gestational age
- Does not confirm a problem — it indicates higher-than-average risk
- Further tests such as NIPT, CVS, or amniocentesis may be discussed
Understanding your NT scan results
NT results are not reported as pass or fail. They are interpreted as part of a risk estimate, which takes into account the NT measurement, your age, and ideally the results of first trimester blood tests. Here is a simple way to understand the two main outcomes:
Lower risk result
- NT measurement within the normal range for gestational age
- Combined risk estimate below the threshold set by your doctor
- Reassuring — routine pregnancy care continues
- A low-risk result does not mean zero risk
Higher risk result
- NT measurement above the expected range
- Combined risk estimate above the threshold
- Further tests will be discussed — NIPT, CVS, or amniocentesis
- Does not confirm a problem — further testing is needed
The NT scan and the double marker test
The NT scan is most powerful when combined with a first trimester blood test called the double marker test (also known as the combined first trimester screen). This blood test measures two hormones — free beta-hCG and PAPP-A — in the mother's blood, and the results are combined with the NT measurement and the mother's age to produce a combined risk estimate.
The combined screen detects approximately 85 to 90 percent of Down syndrome cases with a low false positive rate. Either test alone has a lower detection rate, which is why most specialists recommend doing both in the same window.
- The blood test and NT scan can usually be coordinated at the same visit or within a day or two
- Ask your obstetrician whether a combined screen is advisable for your pregnancy
- NIPT (non-invasive prenatal testing) is a separate, more detailed blood test that can also be considered
What to expect during your NT scan
The NT scan appointment is usually straightforward, though for many parents it carries emotional weight. Knowing what happens beforehand makes the visit much calmer.
Before the scan
- A moderately full bladder is often helpful — confirm when booking
- Bring your previous scan reports, blood test results, and pregnancy records
- Wear comfortable, loose clothing for easy access to the abdomen
- Arrive a few minutes early to complete any registration paperwork
During the scan
- The scan is done over the abdomen; an internal scan may occasionally be needed for a better view
- The whole appointment typically takes 20 to 30 minutes
- The radiologist measures the NT carefully and reviews the heartbeat, anatomy, and position
- At Nitara Scans, every scan is performed personally by Dr. Nayana N Sunku
When to seek medical advice
Speak to your obstetrician or arrange an NT scan promptly if:
- You are between 11 and 14 weeks and have not yet had your NT scan arranged — the window closes quickly
- You have received a higher-risk result and have not yet had follow-up guidance from your doctor
- You have a family history of chromosomal conditions and are planning a pregnancy
- You are considering NIPT and want to understand how it relates to the NT scan
- You have any concerns about the scan findings explained in your report
For most patients the NT scan is a reassuring first look at how the pregnancy is progressing. Getting it done on time and by an experienced radiologist gives you the most accurate information possible at this stage.
Common questions
When exactly should the NT scan be done?
The NT scan must be done between 11 weeks and 13 weeks 6 days. Outside this window the nuchal translucency cannot be measured reliably because the fluid reabsorbs as the pregnancy progresses. Book as soon as your obstetrician advises the timeline.
What does a raised NT measurement mean?
A raised NT does not confirm a chromosomal abnormality. It means the statistical risk is higher than average for your age group, and further testing such as NIPT, chorionic villus sampling, or amniocentesis may be recommended. Many pregnancies with a raised NT go on to be entirely healthy.
Is the NT scan the same as the double marker test?
No. The NT scan is an ultrasound measurement. The double marker test is a blood test. Together they form a combined first trimester screen, which has a significantly higher detection rate than either test on its own.
Can the NT scan detect Down syndrome?
The NT scan is a screening test, not a diagnostic test. It estimates risk — it cannot confirm or rule out Down syndrome. Confirmation requires a diagnostic test such as NIPT, CVS, or amniocentesis, which your doctor will discuss if appropriate.
Do I need a full bladder for the NT scan?
A moderately filled bladder can help early in the window, but this varies depending on your exact gestation. Confirm at the time of booking at Nitara Scans and the team will advise you.
"Had a very good experience with my NT scan with Dr Nayana. She was very patient throughout the scan and all the staff are very polite and friendly. Would highly recommend Nitara scans for best experience."
"Excellent NT Scan (Nuchal Translucency) experience with quick service and accurate reports. This earns 5 stars. Doctors and nurses are very polite and understanding."
NT scan in HSR Layout, Bengaluru
Nitara Scans and Diagnostics offers NT scan and first trimester screening in HSR Layout, Bengaluru. All scans are personally performed by Dr. Nayana N Sunku — DMRD, DNB Radiology, Fetal Medicine Fellow — in a private, calm setting with time for explanation after the scan.