Creator: Dr. Devang Patel
Published: 2026-10-15

In the first trimester, most parents are offered screening for Down syndrome and other chromosomal conditions. Two tests are commonly discussed: the NT scan combined with a blood test (often called the double marker), and cell-free DNA screening, known as NIPT or NIPS. Parents often ask which one is better, or whether one can replace the other. The honest answer is that they do different jobs. Understanding what each one can and cannot tell you makes the choice much easier.

The NT scan with combined screening

The nuchal translucency scan is done between 11 weeks and 13 weeks 6 days. It measures a fluid space at the back of the baby’s neck, and combines that measurement with the mother’s age and a blood test (free beta-hCG and PAPP-A) to calculate the chance of trisomy 21, 18 and 13.

Detects roughly 85 to 90 percent of babies with Down syndrome, with about 5 percent of women receiving a higher-chance result
Confirms the heartbeat, the due date and the number of babies, and whether twins share a placenta
Looks at the baby’s anatomy and can pick up some major structural problems early
Can be combined with uterine artery Doppler and blood pressure to estimate the risk of pre-eclampsia
A thick NT can point to heart problems and genetic conditions even when the chromosomes are normal

NIPT (cell-free DNA screening)

During pregnancy, small fragments of DNA from the placenta circulate in the mother’s blood. NIPT analyses these fragments from a simple blood sample, which can be taken from 10 weeks onwards.

Detects more than 99 percent of babies with Down syndrome, with a false-positive rate below about 0.1 percent
Detection is somewhat lower for trisomy 18 and 13
Is a screening test, not a diagnosis - a high-chance result must be confirmed with CVS or amniocentesis before any decision
In about 1 to 5 percent of tests, no result is obtained (a “no call”), more often in women with a higher weight or very early in pregnancy
Is less reliable after a vanishing twin, in some twin pregnancies, and after donor-egg IVF; it is not suitable after an organ transplant or a recent blood transfusion
Does not assess the baby’s structure, the due date, the placenta or the risk of pre-eclampsia

Pre-natal sex determination is prohibited under the PCPNDT Act. The sex of the baby is not detected or disclosed at any scan.

In keeping with the law, NIPT in India is reported without information on the sex chromosomes that could reveal the sex of the baby.

Why NIPT does not replace the NT scan

Because NIPT looks only at DNA, it cannot see the baby. International bodies, including the Fetal Medicine Foundation, ISUOG, ACOG and FOGSI, advise that a first-trimester ultrasound should still be done when NIPT is chosen. Many serious problems - heart defects, abdominal wall defects, severe skeletal conditions - are not chromosomal and would be missed by a blood test alone. The scan also provides the accurate dating that NIPT depends on.

Ways the tests are combined

NT scan with combined screening for everyone, with NIPT offered when the result is in an intermediate or higher-chance range - a commonly used approach
NT scan plus NIPT together as first-line screening, for parents who prefer the higher detection rate from the start
NIPT first, followed by a detailed 11 to 13 week scan without the double marker
Direct diagnostic testing (CVS from 11 weeks, amniocentesis from 15 weeks) for parents at very high chance or who want a definite answer

Screening is optional. Some parents choose not to have any chromosomal screening, and that choice is respected. Whichever route you choose, the anomaly scan at 18 to 22 weeks is still recommended.

Understanding a higher-chance result

A higher-chance result on either test does not mean the baby has a condition. With the combined test, most women with a higher-chance result have a healthy baby. With NIPT, a high-chance result is more likely to be correct, but false positives occur, partly because the DNA comes from the placenta rather than the baby. The next step is counselling, followed by a diagnostic test if you wish. Never make a decision about the pregnancy on a screening result alone.

A low-chance result on either test is reassuring, but it does not completely rule out a chromosomal or genetic condition. Screening tests look only for specific conditions, and many genetic conditions are not covered. If there is a family history of a genetic disorder, such as thalassaemia, a single-gene condition or a previous child with a developmental problem, ask for genetic counselling early, because different tests may be needed.

Before any test, you should understand what it looks for, what a result would mean for you, and what you would do next. A counselling visit gives you that time. Many couples find that talking through the possibilities in advance makes the results, whatever they are, easier to deal with.

Which test is right for you?

If you want a careful look at the baby, accurate dating and pre-eclampsia screening, the NT scan is essential
If you want a higher detection rate and fewer false alarms for Down syndrome, add NIPT
If you are over 35, had a previous affected pregnancy, or had a higher-chance combined result, NIPT or a diagnostic test is worth discussing
If you are carrying twins, conceived with donor eggs, or had a vanishing twin, discuss the limits of NIPT before choosing it

When to see a doctor

Book your first-trimester consultation early, ideally by 10 to 11 weeks, so there is time to discuss the options and to schedule the NT scan within its window. At Divine Women’s Hospital, Gota, Dr. Devang Patel, who holds Fetal Medicine Foundation (UK) accreditation for the NT scan, performs first-trimester scans and offers counselling on NIPT, diagnostic testing and what the results mean.

More patient guides

This guide is general information for patients and does not replace a consultation with your own doctor.

NIPT or NT scan: which test do you need, and can one replace the other?