What this test measures
The Double Marker measures two pregnancy-specific proteins produced by the placenta: free β-hCG (free beta-human chorionic gonadotropin) and PAPP-A (pregnancy-associated plasma protein A). The values are converted into Multiples of the Median (MoM) for your exact gestational age and combined with three pieces of information — maternal age, the foetal Nuchal Translucency (NT) measurement on ultrasound, and crown-rump length (CRL) — to compute the risk of trisomy 21 (Down syndrome), trisomy 18 (Edward), and trisomy 13 (Patau).
The test is performed between 11 weeks 0 days and 13 weeks 6 days. The result is reported as a risk ratio (e.g. 1 in 1,500). It is a screening test, not a diagnostic test — a "high-risk" result does not confirm the baby is affected; it identifies pregnancies that may benefit from a diagnostic test (NIPT, CVS, or amniocentesis).
Why it matters
Down syndrome occurs in roughly 1 in 800 Indian live births and increases steeply with maternal age. The Double Marker combined with NT ultrasound detects about 85–90% of Down syndrome cases at a 5% false-positive rate — early enough that parents have meaningful time to consider further testing and to discuss outcomes with their obstetrician and a paediatric specialist.
FOGSI and ICMR recommend offering aneuploidy screening to every pregnant woman regardless of age — younger mothers are not exempt from the small but real chance of a chromosomal abnormality. The first-trimester window is preferred because, if the result is high risk, definitive testing (CVS at 11–13 weeks or amniocentesis at 15+ weeks) and decision-making can happen earlier and more safely.
How to prepare
No fasting required. Schedule the blood draw close to your NT scan — ideally within the same 1–2 day window — so the gestational age, CRL, and biochemistry are all interpreted together. Carry your NT scan report, last menstrual period (LMP), and any prior pregnancy history. Smoking, IVF conception, twins, and certain ethnic backgrounds adjust the risk calculation — disclose these on the request form.
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 (range typically 0.5–2.0 MoM) | Low free β-hCG MoM (<0.4) is associated with trisomy 18 and 13. | High free β-hCG MoM (>2.5) is associated with trisomy 21 (Down syndrome) and rarely with molar pregnancy. |
| PAPP-A (mIU/L (or MoM))[1] | Median MoM = 1.0 (range typically 0.5–2.0 MoM) | Low PAPP-A MoM (<0.4) is associated with trisomy 21, 18 and 13 and is an independent risk factor for adverse pregnancy outcomes (pre-eclampsia, IUGR, preterm birth, stillbirth) — even when chromosomes are normal. Many obstetricians flag low PAPP-A for closer growth monitoring. | High PAPP-A MoM is not typically associated with chromosomal abnormality. |
| Risk for Trisomy 21 | Reported as 1 in X (low risk usually ≥ 1 in 250) | — | High-risk (≥ 1 in 250) — recommend further testing with NIPT (cell-free DNA) or diagnostic CVS / amniocentesis. Counselling by an obstetrician and / or geneticist is advised. |
Reading a Double Marker risk score
| Reported risk | Interpretation | Typical next step |
|---|---|---|
| 1 in > 1,000 | Low risk (screen negative) | Routine antenatal care; no further screening needed |
| 1 in 250 – 1,000 | Intermediate risk | Many centres offer NIPT (cell-free DNA) for clarification |
| 1 in < 250 | High risk (screen positive) | Genetic counselling + diagnostic test (NIPT, CVS or amniocentesis) |
| Low PAPP-A (<0.4 MoM) | Even if total risk low — flag for placental insufficiency | Serial growth scans; consider low-dose aspirin |
Frequently asked questions
When is the best time to do a Double Marker test?
Between 11 weeks 0 days and 13 weeks 6 days, paired with the NT (Nuchal Translucency) ultrasound. Ideally schedule them within the same 1–2 day window.
Is the Double Marker a definitive test for Down syndrome?
No. It is a screening test that estimates risk. A "high-risk" result does not mean the baby has Down syndrome — only that further (diagnostic) testing is recommended. About 95% of high-risk results turn out to be normal babies.
What does NIPT add to the Double Marker?
NIPT (cell-free foetal DNA test) is a much more sensitive screen — about 99% detection for Down syndrome with a 0.1% false positive rate. Many obstetricians use NIPT either as the primary screen or as a follow-up to an intermediate Double Marker result.
My PAPP-A is low but my risk is "low" — should I be worried?
A low PAPP-A (<0.4 MoM) even with a low aneuploidy risk is a flag for possible placental insufficiency. Your obstetrician will likely schedule extra growth scans and may start low-dose aspirin to reduce pre-eclampsia risk.
Do I need to fast for the test?
No fasting is needed. You can eat and drink normally.
How does maternal age affect the result?
Down syndrome risk increases sharply with maternal age — roughly 1 in 1,500 at age 20, 1 in 350 at 35, 1 in 100 at 40. The Double Marker combines biochemistry, NT, and your age to give a personalised risk number.
What if I am carrying twins?
The Double Marker can be done in twin pregnancies but interpretation is more complex. Most labs report a single risk per pregnancy. NIPT is increasingly preferred for twins.
If I miss the Double Marker window, what next?
You can do a Quadruple Marker between 15 and 22 weeks. Detection rates are slightly lower (~80% for Down syndrome) but still useful.
Related Pregnancy / Prenatal tests
Tests commonly ordered alongside DOUBLE 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
- RCOG — Antenatal Screening for Down Syndrome · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — First Trimester Screening · accessed 2026-05-30T00:00:00.000Z
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