NT Scan, NIPT & Double Marker — Which Test Is Right for You?

During early pregnancy, many women feel confused about the number of tests recommended—NT scan, Double Marker, NIPT. What do they actually mean, and do you need all of them?

This simple guide helps you understand each test and choose what’s best for you.

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1. What is the NT Scan?

Full form: Nuchal Translucency Scan

When: 11–13+6 weeks

What it checks:

• Fluid thickness behind the baby’s neck (NT)
• Presence of nasal bone
• Early structural markers of chromosomal problems
• Early fetal development (heart, brain, limbs)

Why it’s done:

• Increased NT thickness is associated with Down syndrome, heart defects, and genetic conditions
• Detects many structural problems earlier than the anomaly scan

Is it mandatory?
Yes. Almost every pregnant woman is advised to get an NT scan. It is the foundation of first-trimester screening.

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2. What is the Double Marker Test?

Also called: First-Trimester Combined Screening (FTCS)

When: 11–13+6 weeks

What it checks:

• Free β-hCG
• PAPP-A

These are combined with NT scan findings and maternal age to calculate the risk of:

• Down syndrome (T21)
• Edwards syndrome (T18)
• Patau syndrome (T13)

What it gives:
A risk score (example: 1 in 1,500 = low risk; 1 in 100 = high risk)

Limitations:

• Screening test, not diagnostic
• Accuracy ~82–87%
• Higher false positives compared to NIPT

Who usually chooses it:

• Women under 35 years
• First pregnancy
• No major risk factors
• Cost-sensitive option

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3. What is NIPT?

Full form: Non-Invasive Prenatal Testing

When: Anytime after 10 weeks

What it checks:
Baby’s DNA fragments in mother’s blood to assess risk of:

• Down syndrome (T21)
• Edwards syndrome (T18)
• Patau syndrome (T13)
• Sex chromosome abnormalities (XO, XXY, etc.)
• Some panels also check microdeletions

Accuracy:

• >99% for Down syndrome
• Lowest false-positive rate among screening tests

Advantages:

• Simple blood test
• Most reliable screening method
• Reduces need for invasive tests

Limitations:

• Still a screening test
• Costly
• May fail in obesity, IVF, twins (low fetal fraction)

Who prefers NIPT:

• Women ≥35 years
• Previous affected pregnancy
• Abnormal or borderline NT scan
• High-risk Double Marker result
• IVF or twin pregnancy
• Those wanting maximum reassurance

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So, which test should you choose?

If you want the basic, standard option:
✔ NT Scan + Double Marker

If you are above 35 years or want maximum accuracy:
✔ NT Scan + NIPT

If NT scan shows increased NT or absent nasal bone:
✔ NIPT or consult for diagnostic tests (CVS / Amniocentesis)

If Double Marker comes high-risk:
✔ Follow up with NIPT or Amniocentesis

If you want to avoid invasive tests unless necessary:
✔ NT Scan + NIPT

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What if you are late for the tests?

• NT scan cannot be done after 13+6 weeks
• Double Marker cannot be done later
• NIPT can still be done anytime after 10 weeks
• Next option: Quadruple test (16–20 weeks) + Anomaly scan

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What does a “high-risk” result mean?

A high-risk result does not mean your baby definitely has a problem. It only means the chance is higher than average and further testing may be needed.

Think of it as a warning sign—not a diagnosis.

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What if one test is normal and the other is abnormal?

This can happen.

• NT scan evaluates fetal structure
• Blood tests assess hormone markers

Your doctor will assess the overall risk and may suggest NIPT or a diagnostic test.

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What happens after a high-risk result?

• Repeat or higher-accuracy screening (NIPT)
• Detailed ultrasound
• Diagnostic tests like CVS or amniocentesis (if needed)

All decisions are taken step-by-step with your consent.

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Can chromosomal abnormalities be treated?

Most chromosomal conditions cannot be cured as they involve genetic changes. However, some associated medical problems can be managed after birth.

The goal of screening is informed decision-making and early preparation.

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📍 Source: Dr. Shweta Mehta – DNB, Obstetrics & Gynaecology | United Multispeciality Hospital, Kandivali West, Mumbai.