What this test measures
The triple test measures three substances in maternal blood between 15 and 20 weeks of pregnancy:
• Alpha-fetoprotein (AFP) — made by the fetal liver • Human chorionic gonadotropin (hCG) — made by the placenta • Unconjugated estriol (uE3) — made by the placenta and fetal liver
The lab combines the three values with maternal age, weight, ethnicity, gestational age, diabetic status, and multiple pregnancy status to compute a risk score for Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and open neural tube defects (anencephaly, spina bifida). The result is a probability (e.g. 1 in 500) — not a yes/no diagnosis.
Why it matters
In India, the triple test has been the workhorse second-trimester screening test for years because it is widely available and affordable. It is offered to women who miss the first-trimester combined screen (NT scan + dual marker) or as a complementary test. A "screen-positive" result means a higher-than-cutoff risk and triggers offer of diagnostic testing (amniocentesis or non-invasive prenatal testing — NIPT).
The quadruple test (which adds inhibin A) and the cell-free DNA test (NIPT) have higher sensitivity for Down syndrome (>99% for NIPT vs ~70% for triple). Where NIPT is affordable, it is now preferred. Triple test remains useful where NIPT is not accessible.
How to prepare
No fasting required. Sample is collected between 15 weeks 0 days and 20 weeks 6 days — accuracy is highest at 16–18 weeks. Before testing, an ultrasound is usually done to confirm gestational age (last menstrual period dating may be inaccurate). Provide accurate information about maternal weight, ethnicity, diabetic status, multiple pregnancy, smoking and previous affected pregnancies — these strongly influence the risk calculation.
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 (Alpha-Fetoprotein) (MoM (multiples of median))[1] | 0.5 – 2.5 MoM | Low AFP (< 0.5 MoM): increased risk of Down syndrome or Trisomy 18. Other causes: incorrect dating, fetal demise. | High AFP (> 2.5 MoM): increased risk of open neural tube defects (anencephaly, spina bifida), abdominal wall defects, or incorrect dating. Confirm with detailed ultrasound and amniocentesis if confirmed elevated. |
| hCG (Human Chorionic Gonadotropin) (MoM) | 0.5 – 2.0 MoM | Low hCG: increased risk of Trisomy 18, fetal demise. | High hCG (> 2.0 MoM): increased risk of Down syndrome, also seen in molar pregnancy. |
| Unconjugated Estriol (uE3) (MoM) | 0.5 – 2.0 MoM | Low uE3: increased risk of Down syndrome, Trisomy 18, Smith-Lemli-Opitz syndrome, fetal demise, placental insufficiency. | High uE3: less commonly significant; possible incorrect dating, multiple pregnancy. |
| Calculated Risk (—)[1][2] | Risk < 1:250 for Down syndrome (lab-specific cutoffs vary) | Screen-negative — low risk. Does not rule out chromosomal abnormality. | Screen-positive — increased risk. Recommend NIPT or invasive diagnostic testing (amniocentesis). A screen-positive result is not a diagnosis. |
Triple test patterns in major conditions
| Condition | AFP | hCG | uE3 |
|---|---|---|---|
| Down syndrome (T21) | Low | High | Low |
| Edwards syndrome (T18) | Low | Low | Low |
| Open neural tube defect | High | Normal | Normal |
| Smith-Lemli-Opitz | Low | Low | Very low |
| Normal (unaffected) | Normal | Normal | Normal |
Frequently asked questions
When should I do the triple test?
Between 15 and 20 weeks of pregnancy. Accuracy is highest at 16–18 weeks. If you missed the first-trimester combined screen (NT + dual marker), the triple or quadruple test is your second-trimester option.
A screen-positive result — does it mean my baby has Down syndrome?
No. A screen-positive result means your risk is higher than the cutoff (e.g. 1:200 vs general population 1:500). Most screen-positive pregnancies are normal. Confirmation requires non-invasive prenatal testing (NIPT) or invasive diagnostic testing (amniocentesis).
Is the triple test as accurate as NIPT?
No. The triple test detects ~70% of Down syndrome cases with a 5% false-positive rate. NIPT (cell-free fetal DNA) detects > 99% with < 0.5% false-positive rate. Where NIPT is affordable, it is the preferred non-invasive screen.
What is the difference between triple and quadruple test?
The quadruple test adds inhibin A as a fourth marker, slightly improving Down syndrome detection (~80% vs 70%). Many Indian labs now offer the quadruple as the default second-trimester screen.
Do I need to fast?
No fasting is required.
How long does the report take?
Most NABL labs deliver triple test results in 3–5 days.
What should I do if my AFP is high?
A high AFP raises concern for open neural tube defects. The next step is a detailed (Level II) ultrasound to look at the fetal spine and abdominal wall. If the scan is normal, the risk is reassuringly low; if abnormal, amniocentesis can confirm.
Related Molecular / Genetic tests
Tests commonly ordered alongside Maternal screen (Triple test), or that help interpret an unexpected result.
Sources & references
- ACOG — Prenatal Genetic Screening Tests · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — Triple Screen Test · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Prenatal Screening · accessed 2026-05-30T00:00:00.000Z
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