Quadruple Marker - Second Trimester
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No Fasting Required
Details
Performed between 15 to 20 weeks of pregnancy (commonly at 16–18 weeks) to assess the risk of certain fetal abnormalities
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Quadruple Marker - Second Trimester
- Why is it done?
- Screens for chromosomal abnormalities, particularly Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13) in the fetus
- Assesses risk of neural tube defects such as spina bifida and anencephaly
- Performed during the second trimester of pregnancy, typically between 15 and 22 weeks of gestation
- Used as part of maternal serum screening to identify pregnancies at increased risk for genetic abnormalities
- Recommended for pregnant individuals of all ages, especially those aged 35 or older
- Helps guide decisions regarding further prenatal testing and counseling
- Normal Range
- The Quadruple Marker measures four biochemical markers in maternal blood:
- AFP (Alpha-fetoprotein): Normal range 0.7 - 2.5 MoM (multiples of the median); levels increase with gestational age
- hCG (Human chorionic gonadotropin): Normal range 0.5 - 2.5 MoM; steadily decreases during the second trimester
- uE3 (Unconjugated estriol): Normal range 0.7 - 1.0 MoM; increases progressively throughout the second and third trimesters
- Inhibin A: Normal range 0.5 - 2.5 MoM; remains relatively elevated in the second trimester
- Combined Risk Assessment: Results are typically reported as a risk ratio (e.g., 1 in 250 risk) compared to age-matched population risk
- Negative/Low Risk: Risk ratio greater than 1 in 270 (or other established threshold) indicates low probability of chromosomal abnormality
- Positive/High Risk: Risk ratio less than 1 in 270 indicates increased risk and warrants further testing
- Interpretation
- Down Syndrome (Trisomy 21) Pattern: Elevated hCG, elevated Inhibin A, decreased AFP, and decreased uE3; increases overall risk score
- Edwards Syndrome (Trisomy 18) Pattern: Decreased hCG, decreased AFP, decreased Inhibin A, and decreased uE3; all markers typically low
- Patau Syndrome (Trisomy 13) Pattern: Decreased hCG, elevated AFP, and decreased uE3; variable Inhibin A levels
- Neural Tube Defects (NTD) Pattern: Markedly elevated AFP with normal or near-normal levels of other markers; indicates increased risk for spina bifida or anencephaly
- Factors affecting interpretation: maternal age (critical factor), weight, race/ethnicity, diabetic status, smoking history, and multiple gestations all influence marker levels and risk calculations
- Accuracy: Detects approximately 80% of Down syndrome cases and 60% of Edwards syndrome cases with a false positive rate of 5%
- This is a screening test, not diagnostic; positive results require confirmation with diagnostic testing such as amniocentesis or chorionic villus sampling (CVS)
- Associated Organs
- Primary organ systems involved:
- Fetal chromosomal and genetic material (all cell types affected by chromosomal abnormalities)
- Placenta (produces hCG and Inhibin A)
- Fetal liver (produces AFP)
- Central nervous system (assessed for neural tube defects)
- Conditions commonly associated with abnormal results:
- Down syndrome (Trisomy 21) - cardiac defects, intellectual disability, gastrointestinal malformations
- Edwards syndrome (Trisomy 18) - severe developmental delays, cardiac abnormalities, renal defects, cleft palate
- Patau syndrome (Trisomy 13) - severe malformations, polydactyly, cleft palate, holoprosencephaly
- Spina bifida and anencephaly - neural tube defects affecting spinal cord and brain development
- Other chromosomal abnormalities and genetic syndromes may also affect marker levels
- Follow-up Tests
- For positive or high-risk results:
- Detailed ultrasound examination - comprehensive fetal anatomy scan to assess for structural abnormalities and soft markers
- Cell-free DNA testing (NIPT) - non-invasive prenatal testing for more accurate risk assessment
- Amniocentesis - obtaining fetal cells via needle aspiration for definitive karyotype and chromosomal analysis; typically performed after 15 weeks gestation
- Chorionic villus sampling (CVS) - diagnostic test obtaining placental tissue earlier in pregnancy (10-13 weeks)
- Genetic counseling - discussion of results, options, and implications for pregnancy management
- For specific findings:
- Elevated AFP alone - fetal ultrasound to rule out neural tube defects, multiple gestations, or incorrect dating
- Repeat testing - may be considered if initial results inconclusive or if dating uncertain
- Monitoring and ongoing care:
- Regular prenatal follow-up appointments with obstetric care provider
- Additional third trimester ultrasounds if abnormalities suspected
- Pediatric specialty consultation if fetal anomalies confirmed
- Fasting Required?
- Fasting: No - fasting is not required for this test
- The patient may eat and drink normally before the blood draw
- Patient preparation requirements:
- Accurate gestational age dating is critical - confirm dating via first trimester ultrasound or LMP documentation
- Blood sample collection: simple venipuncture, typically 5-10 mL of maternal blood
- Timing: Blood should be drawn between 15 and 22 weeks of gestation (optimal 15-20 weeks)
- No medications need to be avoided; current medications will not affect test results
- Inform healthcare provider of maternal medical conditions (diabetes, obesity, smoking status) as these may affect marker level interpretation
- Ensure proper specimen labeling with maternal demographic information and gestational age
How our test process works!
