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NT/NB Scan in Pregnancy: Why It’s Important & What to Expect

Dr. Pujil Gulati, IVF Specialist with over 13 years of experience in Assisted Reproductive Techniques BabyBloom IVF Gurgaon

February 6, 2025

Introduction

During pregnancy, various scans and tests ensure the baby’s healthy development. One such crucial scan is the NT/NB scan (Nuchal Translucency/Nasal Bone Scan). This screening test helps detect early signs of genetic abnormalities and assesses the baby’s risk for conditions like Down syndrome, Trisomy 18, and Trisomy 13. Babybloom IVF is the Best IVF Centre in Gurgaon.

In this article, we will discuss the importance, procedure, benefits, risks, and what to expect during an NT/NB scan.

What is NT/NB Scan?

NT Scan (Nuchal Translucency Scan):

The NT scan measures the fluid-filled space at the back of the baby’s neck.
Increased thickness may indicate a risk of genetic disorders.

NB Scan (Nasal Bone Scan):

This scan checks if the baby’s nasal bone is visible.
Absence or underdevelopment of the nasal bone can be a marker for Down syndrome.

Both scans are non-invasive and are performed during the first trimester (between 11 to 14 weeks of pregnancy).

Why is the NT/NB Scan Important?

1. Early Detection of Genetic Disorders

The NT scan helps assess the risk of chromosomal abnormalities like Down syndrome, Edward’s syndrome (Trisomy 18), and Patau syndrome (Trisomy 13).

2. Detecting Heart Defects

An increased NT measurement may indicate congenital heart diseases, allowing early intervention.

3. Nasal Bone as a Key Indicator

The presence or absence of the nasal bone gives additional insights into fetal abnormalities, improving accuracy in risk assessment.

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If abnormalities are detected, parents can consult genetic counsellors and make informed decisions about further testing, such as Non-Invasive Prenatal Testing (NIPT) or Amniocentesis

When is the NT/NB Scan Done?

Best time: Between 11 to 14 weeks of pregnancy.
Ideal NT measurement: Less than 3.5mm (higher values may indicate abnormalities).

How is the NT/NB Scan Performed?

The scan is done using an ultrasound machine.
A transabdominal ultrasound (through the belly) is most common, but in some cases, a transvaginal ultrasound may be required for better clarity.
The doctor measures the nuchal translucency thickness and checks the nasal bone.

What to Expect During the NT/NB Scan?

Preparation for the Scan

You may need to drink water before the scan to ensure a clear image.
No fasting is required.

Procedure

The scan takes around 15-30 minutes.
The technician places gel on the abdomen and uses an ultrasound probe to get images.
You can see your baby on the screen in real-time.

Understanding the Results

Normal NT Range: Below 3.5mm is considered low risk.
Presence of Nasal Bone: A positive sign of normal fetal development.
If results are concerning, the doctor may recommend further tests like NIPT, Chorionic Villus Sampling (CVS), or Amniocentesis.

Is the NT/NB Scan Safe?

Yes, it is 100% safe for both mother and baby.
It is a non-invasive ultrasound scan with no side effects.

What If My NT Scan Shows High Risk?

A high NT measurement does not confirm a genetic disorder but indicates a higher probability.
The doctor may suggest additional genetic tests for accurate diagnosis.

Conclusion

The NT/NB scan is a crucial first-trimester screening that helps detect early signs of genetic conditions, heart defects, and other fetal abnormalities. It is safe, painless, and highly recommended for every pregnant woman. Early detection ensures timely medical decisions and better pregnancy management.

Key Takeaways

NT/NB scan is done between 11-14 weeks.
It helps detect Down syndrome, Trisomy 18, and Trisomy 13.
Normal NT measurement is less than 3.5mm.
The presence of a nasal bone is a positive sign.
If the NT scan shows high risk, further tests like NIPT, CVS, or Amniocentesis may be required.

Frequently Asked Questions (FAQs)

Q. Is the NT/NB scan mandatory?

No, it is optional but highly recommended for early detection of genetic risks.

Q. Can an NT scan be wrong?

NT scans provide risk assessment, not a diagnosis. Further tests are needed for confirmation.

Q. What happens if no nasal bone is seen?

The absence of a nasal bone may indicate Down syndrome, but additional tests are required to confirm.

Q. Does a normal NT/NB scan mean my baby is 100% healthy?

While it reduces the risk of genetic disorders, it does not guarantee the absence of all medical conditions.