PREGNANCY SCREENING Lab Tests

🧪 Quadruple Marker Test – Second Trimester (with Graph Explanation) The Quad Marker Test (or Quadruple Screen) is a prenatal screening test done during the second trimester (15–22 weeks of gestation). It checks the risk of certain fetal chromosomal and structural abnormalities. 📘 What Does It Measure? The test analyzes four key biochemical markers in maternal blood: Marker Full Name Source AFP Alpha-fetoprotein Fetal liver hCG Human chorionic gonadotropin Placenta uE3 Unconjugated estriol Fetal liver and placenta Inhibin A Dimeric inhibin A Placenta and ovaries 📅 When Is It Done? Ideally between 15–18 weeks Can be done up to 22 weeks, but accuracy is best at 16–18 weeks 📊 What Does It Screen For? It does not diagnose, but estimates the risk of: Condition Screening Purpose Trisomy 21 (Down syndrome) Elevated risk detection Trisomy 18 (Edwards syndrome) Detects possible presence Neural Tube Defects (NTDs) Spina bifida, anencephaly 🔍 Interpretation of Results (in MoM – Multiples of Median) Marker Normal MoM High/Low Implications AFP ~1.0 ↑: Neural tube defect ↓: Down syndrome hCG ~1.0 ↑: Down syndrome ↓: Trisomy 18 uE3 ~1.0 ↓: Down syndrome, Trisomy 18 Inhibin A ~1.0 ↑: Down syndrome 📈 Graphical Representation (Simplified Example) Example Result (suggestive of increased risk for Down syndrome): sql Copy Edit Marker MoM | Visual Range (MoM) -------------------|--------------------------------- AFP 0.60 | ▓▓▓▒▒▒ ↓ hCG 2.10 | ▒▒▒▓▓▓▓▓▓ ↑ uE3 0.40 | ▓▓ ↓ Inhibin A 2.30 | ▒▒▒▓▓▓▓▓▓ ↑ Legend: ▓ = Low range ▒ = Borderline ↑ / ↓ = Direction of abnormality 🧠 Pattern Interpretation: ↓ AFP ↑ hCG ↓ uE3 ↑ Inhibin A ➡ Increased risk of Trisomy 21 (Down syndrome) 🎯 Risk Estimates The lab uses your values + maternal factors (age, weight, gestational age, etc.) to calculate risk probability, like: “Risk of Trisomy 21: 1 in 150” (A result under 1:250–1:300 is often considered screen-positive) ⚠️ Factors That Can Affect Accuracy Incorrect gestational age Multiple pregnancies Maternal weight/diabetes Race and ethnicity Smoking 🩺 What If the Test Is Abnormal? A screen-positive result does not mean the baby has a problem. It means further testing is needed, such as: Targeted anomaly scan (Level 2 ultrasound) Non-Invasive Prenatal Testing (NIPT) Amniocentesis (for definitive diagnosis) ✅ Summary Feature Quad Marker Test Timing 15–22 weeks (best: 16–18) Purpose Screen for trisomy 21, 18, NTDs Result Format MoM (Multiples of Median) High-Risk Pattern ↑ hCG, ↑ Inhibin A, ↓ AFP & uE3 Next Steps if Abnormal NIPT, ultrasound, or amniocentesis

🧪 Triple Marker Test – Second Trimester (with Graph Explanation) The Triple Marker Test is a prenatal screening test done during the second trimester (15–20 weeks of gestation) to assess the risk of certain fetal chromosomal and neural tube abnormalities. 📘 What Is the Triple Marker Test? It measures levels of three substances in the mother’s blood: Marker Full Name Source AFP Alpha-fetoprotein Fetal liver hCG Human Chorionic Gonadotropin Placenta uE3 Unconjugated Estriol Fetal liver & placenta Sometimes Inhibin A is added to make it a Quad Marker Test. 📊 What Does It Screen For? The test does not diagnose, but estimates the risk of: Trisomy 21 (Down syndrome) Trisomy 18 (Edwards syndrome) Open Neural Tube Defects (e.g., spina bifida) 📅 When Is It Done? Best performed between 15 and 18 weeks, but can be done up to 20 weeks. 🔍 Interpreting the Results 1. Alpha-Fetoprotein (AFP) Level Interpretation High Risk of neural tube defects (e.g. spina bifida) Low Risk of Down syndrome or Trisomy 18 2. hCG Level Interpretation High Suggests Down syndrome Low Suggests Trisomy 18 3. uE3 Level Interpretation Low Suggests Down syndrome or Trisomy 18 📈 Graph Explanation (MoM – Multiples of Median) Test results are usually expressed as MoM (Multiples of the Median). A value of 1.0 MoM is average for gestational age. Normal range: ~0.5–2.5 MoM for each marker Graph typically shows MoM values plotted against reference ranges Here's a simplified diagram: sql Copy Edit MoM ↑ | ◯ = Normal Range | AFP hCG uE3 |------------------- | |◯| |↑| |↓| | AFP normal hCG elevated uE3 decreased 🧠 This pattern is suggestive of increased risk for Down syndrome. 🧾 Factors Affecting Accuracy Incorrect gestational age Maternal weight Multiple pregnancy (twins, etc.) Diabetes Ethnicity These factors are considered during risk calculation. 🩺 What If Risk Is High? A high-risk result does not confirm a problem. Next steps may include: Detailed ultrasound (anomaly scan) Non-invasive prenatal testing (NIPT) Amniocentesis (for definitive diagnosis)