NIPT vs combined screening: which test is right for you?

Medically written by Dr. Sushma Dhakal, MBBS · MD (Obstetrics & Gynaecology) · Fellowship in Fetal Medicine · Updated 30 October 2026 · 3 min read

Many parents ask whether they should choose the combined test or NIPT to screen for conditions such as Down syndrome. Both are safe for the pregnancy, and both are screening tests. They estimate the chance of a condition but do not give a final diagnosis.

The combined test

The combined test is done at 11 weeks to 13 weeks 6 days. It combines the NT measurement from the scan, a maternal blood test (free β-hCG and PAPP-A) and the mother's age. It detects about 90% of babies with Down syndrome (trisomy 21), with about 5% of pregnancies screening "high chance". It also screens for trisomies 18 and 13.

An important benefit is the scan itself: an experienced specialist can see some major structural problems at this stage, and the same visit can include screening for pre-eclampsia.

NIPT (non-invasive prenatal testing)

NIPT analyses small fragments of the baby's DNA (mostly from the placenta) in the mother's blood. It can be done from 10 weeks.

It detects more than 99% of babies with Down syndrome, and most babies with trisomies 18 and 13, with a false-positive rate below 0.1%.
Some panels also report sex chromosome conditions or certain small deletions, but these results are less reliable.
In about 1–5% of samples no result is obtained, often because the fetal DNA fraction is low; a repeat sample is then needed.
NIPT is more expensive than the combined test and is usually sent to a specialised laboratory.

What neither test does

Neither test can confirm a diagnosis. A high-chance result should be confirmed with CVS or amniocentesis before any decision is made, because placental changes (mosaicism) can cause false results.
Neither replaces the NT scan or the anomaly scan. NIPT does not look at the baby's structure, so a detailed 11–14 week scan is still recommended even if you choose NIPT.
A low-chance result is reassuring but does not exclude every genetic or developmental condition.

Which should I choose?

There is no single right answer. Common approaches are:

Combined test for everyone, with NIPT offered as a second step if the chance is high or intermediate.
NIPT first, together with an early detailed scan, for families who prefer the highest screening accuracy.
If the NT scan shows a clearly increased NT or a structural problem, diagnostic testing (CVS or amniocentesis with microarray) is usually more informative than NIPT.

Screening is always optional. Genetic counselling before testing helps you understand what each result could mean and choose what feels right for your family.

Have questions about your pregnancy?

Book a consultation with Dr. Sushma Dhakal, Fellowship-trained fetal medicine specialist (FMF UK certified).

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Frequently asked questions

Is NIPT a diagnostic test?

No. It is a highly accurate screening test. A high-chance result should be confirmed by CVS or amniocentesis.

Do I still need the NT scan if I have NIPT?

Yes. The 11–14 week scan checks the baby's structure and dating, which NIPT cannot do.

When can NIPT be done?

From 10 weeks of pregnancy. The combined test is done between 11 weeks and 13 weeks 6 days.

Is NIPT safe for the baby?

Yes. It needs only a blood sample from the mother.

This guide is for general information only and is not a substitute for personal medical advice. Every pregnancy is different. Please consult your doctor about your own situation. In an emergency, go to the nearest hospital.