Double marker vs quad marker vs NIPT: which screening test does what?
In short
- Double marker, quad marker and NIPT all screen for Down's syndrome and similar conditions.
- None of them can diagnose on its own — they only give a chance.
- Double marker is at 11 to 13 weeks. Quad is at 15 to 22 weeks. NIPT is from 10 weeks.
- A higher-chance result on any of them usually leads to a follow-up test to check further.
What happens
- Ask your doctor which of these tests is available to you, and when in your pregnancy it needs to be done.
- Have the blood sample (and ultrasound, if it's the double marker/combined test) taken in the recommended window.
- Discuss your chance result with your doctor, and whether a diagnostic test is right for you if your chance comes back higher.
The details: numbers and where they differ
Side by side
The double marker test measures two blood markers (free beta-hCG and PAPP-A) around 11 to 13 weeks, usually alongside the NT ultrasound scan. The quad marker test measures four blood markers later, between 15 and 22 weeks, and also screens for neural tube defects, which the first-trimester tests don't. NIPT analyses fragments of your baby's DNA circulating in your blood, can be done from 10 weeks, and is generally the most sensitive of the three — but it is still a screening test, not a diagnosis, and a positive result needs confirming.
In the source's own words
NIPT is a screening test, not a diagnostic one, and it can produce both false positive results (indicating increased risk when the fetus is unaffected) and false negative results (indicating decreased risk when the fetus is actually affected). A positive (high-risk) NIPT result should be followed by diagnostic testing to confirm the finding before a genetic condition is considered established.
MedlinePlus Genetics (NIH/National Library of Medicine), Noninvasive prenatal testing (NIPT). Quoted verbatim.
The numbers
| Measure | Value | Source |
|---|---|---|
| Double marker (dual marker) test window, India (pregnant women, India) | 11–13 weeks gestation | Peer-reviewed Indian obstetric literature (PMC-hosted) |
| Quad marker screening window (pregnant women (ACOG, US)) | 15–22 weeks gestation | American College of Obstetricians and Gynecologists (ACOG) |
| NIPT / cell-free DNA earliest window (pregnant women) | ≥10 weeks gestation | MedlinePlus Genetics (NIH/National Library of Medicine) |
When to call your doctor
- If you're unsure which test you've been offered or when it needs to happen.
- If any of these tests comes back higher-chance and you want to discuss a diagnostic test.
Discuss your results with your doctor: this page reports what these sources say, not advice for your situation.
Sources
- Peer-reviewed Indian obstetric literature (PMC-hosted), Down's Syndrome Screening in the First Trimester with Additional Serum Markers: Indian Parameters. Named as the guideline this section describes; its text and tables are not reproduced here (Journal article; licence not confirmed (cite only)). Describes the double marker test's usual window (11 to 13 weeks) and the two markers it measures.
- American College of Obstetricians and Gynecologists (ACOG), Prenatal Genetic Screening Tests (Patient FAQ). Named as the guideline this section describes; its text and tables are not reproduced here (All rights reserved (cite only)). Describes the quad test's four markers, conditions screened and 15-to-22-week window.
- MedlinePlus Genetics (NIH/National Library of Medicine), Noninvasive prenatal testing (NIPT). Quoted verbatim. US federal government work, public domain.
Sources checked 2026-09-26. How we source and check every page.
Educational summary of named sources, not medical advice.