Triple Marker Test: Timing, Normal Values and How to Read Your Risk Result
The triple marker test is a second-trimester screening test performed between 15 weeks 0 days and 20 weeks 6 days of pregnancy. It measures Alpha-Fetoprotein (AFP), total hCG, and Unconjugated Oestriol (uE3) in maternal blood to estimate the risk of Down syndrome, Edwards syndrome, and open neural tube defects such as spina bifida.
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The triple marker test is a second-trimester maternal blood screening test performed strictly between 15 weeks 0 days and 20 weeks 6 days (ideally 16 to 18 weeks). It measures three serum markers: Alpha-Fetoprotein (AFP), total human chorionic gonadotrophin (hCG), and Unconjugated Oestriol (uE3).
Combined with maternal age, weight, exact gestational age dated by ultrasound, and diabetic status, it calculates probability risk figures for Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and open neural tube defects (NTDs) such as spina bifida and anencephaly.
If the first-trimester double marker window was missed, the triple marker or quadruple marker test provides essential second-trimester biochemical risk evaluation before the 18–22 week anomaly scan.
Clinical Significance
The triple marker test provides second-trimester risk assessment when the first-trimester screening window (11–13.6 weeks) was missed. Elevated AFP (>2.0 or 2.5 MoM) screens for open neural tube defects (spina bifida, anencephaly) and abdominal wall defects. Low AFP (<0.5 MoM), elevated hCG (>2.0 MoM), and low uE3 (<0.5 MoM) indicate an increased risk of Down syndrome.
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Reference Ranges — Triple Marker Test: Timing, Normal Values and How to Read Your Risk Result
NABL-validated intervals · Adults · values may vary by age & sex
| Parameter / Group | Range | Unit | Status |
|---|---|---|---|
| AFP (Unaffected Pregnancy) | 0.5 – 2.0 | MoM | Normal |
| AFP (Neural Tube Defect Risk)Elevated; risk of spina bifida / anencephaly | > 2.0 | MoM | Abnormal |
| AFP (Down Syndrome Pattern)Decreased level associated with trisomy 21 | < 0.5 | MoM | Abnormal |
| Total hCG (Unaffected) | 0.5 – 2.0 | MoM | Normal |
| Total hCG (Down Syndrome)Elevated level associated with trisomy 21 | > 2.0 | MoM | Abnormal |
| Unconjugated Oestriol (uE3) | 0.5 – 2.0 | MoM | Normal |
| Unconjugated Oestriol (uE3 Low)Decreased in Down syndrome & trisomy 18 | < 0.5 | MoM | Abnormal |
| Trisomy 21 Risk — Screen Negative | < 1 in 250 | Ratio | Normal |
| Trisomy 21 Risk — Screen PositiveHigh risk result — genetic counselling recommended | > 1 in 250 | Ratio | Abnormal |
⚕️ Reference ranges are population-based guidelines. Results must be interpreted in clinical context by a qualified physician. Always consult your doctor before making healthcare decisions.
Frequently Asked Questions
Q: When should the triple marker test be performed?
A: Between 15 weeks 0 days and 20 weeks 6 days of pregnancy, with 16 to 18 weeks being the optimal window. Accurate dating by ultrasound is essential for MoM calculation.
Q: What does the triple marker test screen for?
A: It screens for Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and open neural tube defects (such as spina bifida and anencephaly).
Q: What is the difference between double marker and triple marker?
A: Double marker is done in the first trimester (11–13.6 weeks) with PAPP-A, free beta-hCG, and NT scan. Triple marker is done in the second trimester (15–20 weeks) with AFP, total hCG, and uE3, and includes neural tube defect screening.
Q: What does a high AFP result mean on triple marker?
A: An AFP above 2.0 or 2.5 MoM suggests an increased risk of open neural tube defects (spina bifida) or abdominal wall defects. It warrants a targeted high-resolution ultrasound anomaly scan.
Q: Do I need to fast for a triple marker test?
A: No, fasting is not required. What the laboratory requires is accurate gestational age from an ultrasound scan, maternal weight, age, and diabetes status.
Q: What is a normal triple marker result?
A: A calculated risk below 1 in 250 for Down syndrome, and an AFP level below 2.0 MoM for neural tube defects, reported as screen negative.
Q: Is the triple marker or quadruple marker better?
A: The quadruple marker is superior because it adds Inhibin A, improving Down syndrome detection rates to 75–81% compared to approximately 65–70% for the triple marker.
Q: Does a high risk result mean my baby has a birth defect?
A: No. It is a screening probability estimate. Most women with a high-risk result have healthy, normal babies. Further evaluation includes genetic counselling, cell-free DNA (NIPT) screening, a targeted level-II ultrasound, or diagnostic confirmation via amniocentesis.
Q: Can triple marker test be done in twin pregnancies?
A: Yes, but marker levels are higher due to two placentas, requiring specialized twin algorithms. Interpretation carries higher uncertainty than in singletons.
Q: What should I do if my triple marker test is high risk?
A: Consult your obstetrician for genetic counselling. Recommended follow-up steps include a high-resolution level-II anomaly scan at 18–22 weeks, NIPT, or diagnostic amniocentesis.
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The triple marker test remains a vital second-trimester screen. If a patient missed the first-trimester double marker, the triple or quadruple test provides essential risk calculation for Down syndrome and open neural tube defects before the 18–22 week anomaly scan.
Clinically reviewed · October 2026 · QXL Diagnostics NABL Lab
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