NT/NB Scan: Importance, Procedure, and What to Expect
Medically Reviewed By
Prof. Ashok Rattan
Written By Muskan Taneja
on Feb 18, 2025
Last Edit Made By Muskan Taneja
on Feb 18, 2025
Did you know that every year, approximately 30,000 to 35,000 babies in India are born with Down syndrome? This equates to about 1 in every 800 to 850 births.
Down syndrome is one of the most common chromosomal conditions in newborns, and it can be detected before birth through prenatal screenings such as the NT/NB scan. If your healthcare provider has recommended an NT/NB scan, congratulations, you've come to the right place.
This comprehensive guide will provide details about the NT/NB scan, its importance, its procedure, and what to expect from the scan.
What is an NT/NB Scan?
The full form of the NT NB scan is the Nuchal Translucency/Nasal Bone scan. It is a non-invasive ultrasound that assesses the risk of chromosomal abnormalities in a fetus. Babies with abnormalities tend to have increased fluid accumulation at the back of their neck in the first trimester, leading to a larger-than-average nuchal translucency space.
| Purpose | To check the risk of chromosomal abnormalities such as Edwards syndrome and Down syndrome. |
| NT NB Scan Full Form | Nuchal Translucency/ Nasal Bone Scan |
| Preparation | Wear loose, comfortable clothing, and avoid applying lotions or creams on your abdomen before the scan. |
| Result | The NT scan report indicates a ‘low-risk’ or ‘high-risk.’ |
| Risk | There is no risk associated with the scan. |
| Cost | The NT/NB scan costs from INR 1,000 to INR 2,000, depending on the city, available discounts, and the diagnostic center. |
Key Aspects of NT/NB Scan
An NT and NB scan are often combined for a prenatal screening test. It provides insights about your baby’s health. But, before heading ahead, learn about its key aspects.
- NT Scan: This measures the nuchal translucency, the fluid-filled space at the back of the baby's neck. An increased NT measurement may indicate a higher risk of chromosomal abnormalities.
- NB Scan- The NB scan checks for the presence of nasal bones. These are two small and symmetrical bones that form the bridge of your nose, located in the middle of your face and between the frontal processes of the maxilla. The absence of nasal bone may indicate a sign of a chromosomal condition.
- Blood Flow in Tricuspid Valve and Ductus Venosus- A healthcare professional analyzes the blood flow in these two veins to check for potential abnormalities. The ductus venosus is a vessel in the baby’s life, and the tricuspid valve is in the baby’s heart.
An Important Fact:
Along with checking for potential chromosomal abnormalities, the NT/NB scan can also visualize multiple fetuses in the uterus, making it a useful tool for confirming a twin pregnancy.
Importance of the NT/NB Scan
The NT NB scan is important in pregnancy for detecting abnormalities in the fetus. Let’s understand that.
- The scan can assess the risk of genetic conditions like Edwards, Down, and Patau.
- It can assess the chromosomal and structural health of your developing fetus.
- The scan can examine the fetal nose and palate.
- It can measure the fetal heart rate and the collection of fluid.
- The NT measures the fluid-filled space at the back of your baby's neck. A thick NT can be associated with an increased risk of chromosomal abnormalities.
- NB checks for the presence or absence of nasal bone for potential chromosomal issues.
- Early detection of chromosomal abnormalities helps assess the risk and plan a personalized approach.
- Altogether, this screening reassures expectant parents and boosts confidence in their baby’s healthy development.
Also, read https://redcliffelabs.com/myhealth/radiology/nt-scan-purpose-procedure-and-results/
What Does the NT/NB Scan Measure?
The NT NB scan measures the nuchal fold thickness, an area of tissue at the back of an unborn baby's neck. More fluids in this area determine your fetus's risk of having chromosomal abnormalities like Down syndrome, Edwards syndrome, and Patau syndrome.
A higher NT measurement may show an increased risk for congenital heart conditions. Besides, it can also screen for some basic anatomical structures in your unborn fetus.
Who Should Get the NT NB Scan?
An NT/NB scan is essential for all pregnant women in their first trimester. However, some people should prioritize getting this scan.
- Women aged 35 years or older.
- Women who have a family history of chromosomal abnormalities.
- Women whose previous child is born with a chromosomal abnormality.
- Expecting parents are concerned about their baby's health.
Preparation for the NT NB Scan
The NT/NB scan is a non-invasive ultrasound that requires minor preparations.
- Stay Hydrated: Drink 8-10 glasses of water daily.
- Wear Comfortable Clothes: A healthcare professional will apply the ultrasound gel for scanning. So, wear comfortable clothes and avoid applying any cream or lotion on the abdomen area.
- Talk to Your Doctor: Inform your doctor if you have a family history of genetic conditions.
- Be Calm: It is a painless screening method. So, stay relaxed and calm, and be comfortable for a smooth procedure.
What is the Procedure for an NT NB Scan?
The scan measures the clear space in the tissue at the back of the baby's neck and evaluates the development of the nasal bone.
- Ultrasound Examination- A healthcare professional will apply ultrasound gel to your abdomen and use an ultrasound transducer to capture images of your baby.
- Measurement of NT- The healthcare provider will measure the fluid-filled space at the back of the baby’s neck.
- Assessment of Nasal Bone- The provider will check for the presence or absence of the nasal bone to assess the risk of chromosomal abnormalities.
Are There Any Risks Associated with the Scan?
There are no risks associated with the NT NB scan in pregnancy. The NT/NB scan is completely safe for both mother and baby. It uses ultrasound technology, which involves no radiation and is widely accepted for use during pregnancy.
When is the NT/NB Scan Done?
NT NB scan is an important scan for every pregnant woman. A common question is: When should you take this scan?
The ideal time for the scan is during the first trimester, specifically between weeks 11 through 14 of pregnancy.
Understanding the NT/NB Scan Results
A normal fluid level indicates a lower risk of chromosomal conditions, whereas an increased level suggests a higher likelihood of genetic or congenital abnormalities.
It is not a conclusive result and, in most cases, your doctor may offer a blood test to improve the accuracy of the screening. It’s important to note that NT scans are screening tools that estimate the likelihood of a condition rather than providing a definitive diagnosis.
How are NT NB Scan Results Calculated?
Your baby's chance of chromosomal abnormality is determined by your age, your baby's gestational age, the NT measurement, and the blood test results.
Age has a major role in increasing the chances of a baby with a chromosomal abnormality. For example- the chances of Down syndrome are 1 in 1,200 at age 25 and 1 in 100 at age 40.
How Accurate is the NT/NB Scan?
The NT/NB scan has an accuracy rate of approximately 70% in detecting abnormalities. However, when combined with a first-trimester blood test, its accuracy increases to about 95%.
What is the NT NB Scan Normal Range?
A normal NT measurement is typically less than 3.5 mm. A measurement above this may indicate an increased risk of congenital abnormalities.
A normal range means there are lower chances of genetic or chromosomal abnormalities in your fetus. However, to confirm the results, your doctor may recommend additional tests, like the Double Marker Test.
Certain factors that may affect the results are:
- Not definitive
- Negatives or false positives
- Early detection timing may influence measurement accuracy.
- While focusing on one condition, the test may not detect other abnormalities or diseases.
What does an Abnormal NT NB scan result mean?
If your screening is abnormal, your doctor will discuss options like chorionic villus sampling (CVS) or amniocentesis to diagnose the condition. They may also look at the fetal heart with a fetal echocardiogram (ECG). Additionally, they may also refer you to a genetic counselor to better understand the condition.
- CVS- A sample of tissue is taken from your placenta and tested for genetic conditions.
- Amniocentesis- A needle is used to draw amniotic fluid from your uterus. This fluid contains cells that contain genetic information to diagnose abnormalities or infectious conditions.
Your healthcare provider may recommend the double marker test along with the NT scan to confirm the results. If they do, you can get it from India’s leading diagnostic service provider, Redcliffe Labs at an affordable price and with a home sample collection service.
Steps to Book a Test from Redcliffe Labs
- Visit the website www.redcliffelabs.com
- Search for the test you need.
- Fill out your details: name, preferred time, date, and address.
- Make the payment.
- A phlebotomist will visit your home for the sample collection.
Note: You will receive a confirmation through SMS or WhatsApp.
Does an Abnormal NT NB Scan Mean Your Baby Has Down Syndrome?
No, an abnormal NT NB scan doesn’t directly mean your fetus has Down syndrome or any other congenital syndrome. It may also showcase that your fetus is at a higher risk of having these conditions.
The Bottom Line
An NT NB scan can help determine if your baby has a congenital or genetic abnormality. Further, don’t worry if you have an irregular result. Consult with your doctor and they will recommend the next step, such as genetic counseling and further testing.
FAQs
Ques1 What is an NT NB scan in pregnancy?
Ans1 It is a prenatal non-invasive screening test that assesses the risk of chromosomal abnormalities in your fetus.
Ques2 When is the NT NB scan done?
Ans2 The recommended week for the scan is between the 11th week and the 13th week of pregnancy.
Ques3 Is the NT NB scan painful?
Ans3 No, the scan is not painful. It is a non-invasive prenatal screening performed through an ultrasound.
Ques4 How long does the NT NB scan take?
Ans4 The NT scan typically takes 20-30 minutes. However, if your baby is in an awkward position, the process may take longer to capture clear images.
Ques5 Can the NT NB scan harm the baby?
Ans5 The NT scan is completely safe for the baby or the mother.
