What this test measures
The Triple Marker measures three substances in maternal serum: AFP (alpha-fetoprotein from the foetal liver), uE3 (unconjugated estriol from the foeto-placental unit), and β-hCG (from the placenta). Each is expressed as a Multiple of the Median (MoM) for the exact gestational age. Combined with maternal age, weight, ethnicity, and diabetes status, the values generate a calculated risk for trisomy 21 (Down syndrome), trisomy 18, and open neural tube defects.
The test is done between 15+0 and 22+0 weeks of gestation. Down syndrome detection is ~70% at a 5% false-positive rate — lower than the Quadruple Marker (which adds Inhibin A to push detection up to ~80%) and lower than first-trimester combined screening (~85–90%). The Triple Marker remains in use for cost reasons and where Quad is not available.
Why it matters
For Indian patients who present after 13+6 weeks and where cost is a major concern, the Triple Marker offers a still-meaningful screen for Down syndrome and neural tube defects at a price point below the Quadruple Marker. ACOG no longer recommends Triple Marker as a first-line option (preferring Quad or NIPT) but it is still widely available in Indian labs.
The AFP component is particularly useful because it detects ~80% of open neural tube defects (spina bifida, anencephaly) — something the first-trimester Dual Marker cannot do. Even when first-trimester screening was performed, some obstetricians order a separate AFP at 16–18 weeks specifically for NTD screening.
How to prepare
No fasting required. Schedule between 15+0 and 22+0 weeks (ideal 16–18 weeks). Bring an accurate gestational age (LMP or dating scan), and disclose IVF/IUI, ethnicity, weight, diabetes status, and twins 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 |
|---|---|---|---|
| AFP (IU/mL (or MoM))[1] | Median MoM = 1.0 | Low MoM associated with trisomy 21 and trisomy 18. | High MoM (≥2.5) associated with open neural tube defects, abdominal wall defects, multiple gestation, or incorrect gestational dating. |
| uE3 (Unconjugated Estriol) (ng/mL (or MoM)) | Median MoM = 1.0 | Low MoM associated with trisomy 21, trisomy 18, and rare metabolic / placental disorders. | High MoM not typically associated with chromosomal abnormality. |
| β-hCG (mIU/mL (or MoM)) | Median MoM = 1.0 | Low MoM associated with trisomy 18. | High MoM (>2.5) associated with trisomy 21. |
| Calculated risk for Trisomy 21 | Low risk ≥ 1 in 270 | — | ≥ 1 in 270 = screen positive. Counsel for NIPT or amniocentesis. |
Triple Marker pattern by condition
| Condition | AFP | uE3 | β-hCG |
|---|---|---|---|
| Unaffected pregnancy | Normal | Normal | Normal |
| Trisomy 21 (Down) | ↓ | ↓ | ↑ |
| Trisomy 18 (Edward) | ↓ | ↓ | ↓ |
| Open neural tube defect | ↑↑ | Normal | Normal |
| Multiple pregnancy | ↑ | Normal/↑ | ↑ |
| Wrong gestational age | Variable | Variable | Variable |
Frequently asked questions
How does the Triple Marker compare to the Quadruple Marker?
The Quad Marker adds Inhibin A as a fourth marker. This raises Down syndrome detection from ~70% (Triple) to ~80% (Quad) at the same false-positive rate. Most modern centres prefer the Quad if available.
When is the Triple Marker done?
Between 15+0 and 22+0 weeks, ideally at 16–18 weeks.
I already did the Dual Marker — do I need the Triple too?
Not for chromosomes. But the Dual Marker does not include AFP, so a stand-alone AFP at 16–18 weeks can add value for neural tube defect screening. A detailed anomaly scan at 18–22 weeks remains the other key check.
Do I need to fast?
No.
My risk shows 1 in 150 — what does that mean?
1 in 150 is above the 1 in 270 cutoff, so it is reported as "screen positive". This does not confirm Down syndrome; it means your calculated risk is high enough to warrant a discussion about NIPT or amniocentesis. About 95% of "screen positive" Triple Marker results turn out to be unaffected babies.
What does a high AFP suggest?
A high AFP (≥2.5 MoM) can indicate an open neural tube defect (spina bifida, anencephaly), an abdominal wall defect, multiple pregnancy, or wrong dating. An anomaly scan is the next step.
Can the Triple Marker be done in twins?
Yes but accuracy is lower. NIPT is generally preferred for twin pregnancies.
Is this still a useful test in 2026?
It is no longer first-line in most international guidelines, but it remains widely available and affordable. If the Quadruple Marker or NIPT are accessible, those are preferred.
Related Pregnancy / Prenatal tests
Tests commonly ordered alongside TRIPLE MARKER, or that help interpret an unexpected result.
Sources & references
- ACOG — Screening for Fetal Chromosomal Abnormalities · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — Maternal Serum AFP Test · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — Second Trimester Screening · accessed 2026-05-30T00:00:00.000Z
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