What this test measures
The Dual Marker (synonymous with Double Marker in Indian lab nomenclature) measures two placenta-derived proteins: free β-hCG and PAPP-A (pregnancy-associated plasma protein A). The values are expressed as Multiples of the Median (MoM) for your gestational age and combined with maternal age, foetal nuchal translucency (NT), and crown-rump length (CRL) to generate a personalised risk for trisomy 21 (Down syndrome), trisomy 18 (Edward), and trisomy 13 (Patau).
It is performed between 11+0 and 13+6 weeks of gestation. Results are reported as a risk ratio (e.g. 1 in 1,500). The test is a screen, not a diagnosis — high-risk results are confirmed with NIPT, CVS, or amniocentesis.
Why it matters
Indian aneuploidy screening practice follows international guidelines — FOGSI and ICMR both recommend the Dual Marker (with NT) as the standard first-trimester screen for every pregnancy, irrespective of maternal age. Detection rate for Down syndrome is 85–90% at a 5% false-positive rate. Doing the screen in the first trimester gives parents time for follow-up diagnostic testing and decisions if needed.
Low PAPP-A is also clinically important even when chromosomal risk is low — it predicts pre-eclampsia, foetal growth restriction, preterm birth, and stillbirth. Many obstetricians use a low PAPP-A to start prophylactic low-dose aspirin and to add growth scans through the pregnancy.
How to prepare
No fasting required. Schedule the blood draw close to your NT scan (within 1–2 days) so the biochemistry and ultrasound markers are interpreted together. Bring your scan report, LMP date, and any prior pregnancy history. Inform the lab if the pregnancy is from IVF, if there are twins, your smoking status, and ethnicity — all adjust the calculated risk.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Free β-hCG (ng/mL (or MoM))[1] | Median MoM = 1.0 | Low free β-hCG MoM is associated with trisomy 18 and 13. | High free β-hCG MoM (>2.5) is associated with trisomy 21. |
| PAPP-A (mIU/L (or MoM))[1] | Median MoM = 1.0 | Low PAPP-A MoM (<0.4) is associated with trisomies and with placental dysfunction (IUGR, pre-eclampsia, preterm birth) even when the karyotype is normal. | High PAPP-A is not typically associated with chromosomal abnormality. |
| Calculated risk for Trisomy 21 | Low risk typically ≥ 1 in 250 | — | ≥ 1 in 250 = high risk. Counselling + NIPT or diagnostic test (CVS/amniocentesis) is recommended. |
Dual Marker risk bands
| Risk score | Category | Next step |
|---|---|---|
| 1 in > 1,000 | Low risk | Routine antenatal care |
| 1 in 250–1,000 | Intermediate | NIPT for clarification |
| 1 in < 250 | High risk | Genetic counselling + diagnostic test |
| Low PAPP-A (<0.4 MoM) only | Placental flag | Serial growth scans ± low-dose aspirin |
Frequently asked questions
Is the Dual Marker different from the Double Marker?
No — they are the same test (free β-hCG + PAPP-A with NT scan). The terms are used interchangeably across Indian labs.
When is it done?
Between 11 weeks 0 days and 13 weeks 6 days, paired with the NT ultrasound.
Will the test confirm if my baby has Down syndrome?
No. It only estimates risk. A high-risk result needs a diagnostic test (NIPT, CVS or amniocentesis) for confirmation.
Do I need to fast?
No fasting is needed.
My result says 1 in 800 — is that low or high risk?
1 in 800 is generally considered low risk (most labs use 1 in 250 as the cutoff). However, if your background age risk was 1 in 1,500, a result of 1 in 800 is a meaningful shift and your doctor may discuss further options.
What if I miss the 13+6 week window?
You can opt for the Quadruple Marker between 15 and 22 weeks, or directly for NIPT (which works any time after 10 weeks).
Can the test detect neural tube defects?
No. The Dual Marker does not include AFP and cannot screen for neural tube defects (spina bifida, anencephaly). The Quadruple Marker (with AFP) and a detailed anomaly scan at 18–22 weeks do.
How accurate is it?
When combined with NT, the detection rate for Down syndrome is 85–90% at a 5% false-positive rate. NIPT is more accurate (>99% detection) but more expensive.
Related Pregnancy / Prenatal tests
Tests commonly ordered alongside DUAL MARKER, or that help interpret an unexpected result.
Sources & references
- ACOG — Screening for Fetal Chromosomal Abnormalities · accessed 2026-05-30T00:00:00.000Z
- Fetal Medicine Foundation — 11–13 Weeks Scan · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — First Trimester Screening · accessed 2026-05-30T00:00:00.000Z
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