Quad Screen (Maternal Serum Screening): A Complete Guide
Quad Screen or Quadruple Marker Test is a second-trimester maternal blood test offered between 15–22 weeks of pregnancy. It helps assess the likelihood of specific chromosomal and neural tube defects in the fetus.
🧬 Markers Measured in Quad Screen
- AFP (Alpha-fetoprotein): Low levels can suggest Down syndrome; high levels may indicate neural tube defects.
- hCG (Human chorionic gonadotropin): High levels may point to increased risk of Down syndrome.
- uE3 (Unconjugated estriol): Low levels may suggest chromosomal problems like Trisomy 18.
- Inhibin A: Often elevated in pregnancies affected by Down syndrome.
🗓️ When to Perform the Quad Screen?
Best performed between 16 and 18 weeks of gestation. No fasting is required. Accurate dating via ultrasound increases test reliability.
📊 Interpretation of Results
| Condition | AFP | hCG | uE3 | Inhibin A |
|---|---|---|---|---|
| Down Syndrome | ↓ | ↑ | ↓ | ↑ |
| Trisomy 18 | ↓ | ↓ | ↓ | ↓ or Normal |
| Neural Tube Defect | ↑ | Normal | Normal | Normal |
🧪 What Happens If The Result Is Abnormal?
The Quad Screen is a screening—not diagnostic—test. If the results are abnormal, your doctor may recommend:
- Targeted Ultrasound for fetal anatomy
- Non-Invasive Prenatal Testing (NIPT)
- Amniocentesis for genetic confirmation
🔍 Risk Calculation Factors
- Mother's age
- Gestational age (from ultrasound)
- Weight
- Ethnicity
- Diabetes status
💡 Benefits of the Quad Screen
- Non-invasive and safe for both mother and baby
- Can help guide further diagnostic steps
- Important for women who missed first-trimester tests
📎 Related Articles
📥 Download Summary
Click here to download the Quad Screen PDF Summary
❓ FAQs
Q: Is the Quad Screen mandatory?
A: No. It is optional but recommended as a part of prenatal care.
Q: Does the Quad Screen detect all genetic disorders?
A: No. It mainly screens for Down syndrome, Trisomy 18, and NTDs.
Q: Can the test be done in IVF pregnancies?
A: Yes, with accurate details entered into the risk algorithm.
Author: Dr. Pawan Gaba | LabDecoded
📅 Published: May 2025 | 🔁 Updated: May 2025
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