The Quadruple Test (also called Quad Screen or Quad Marker Test) is a prenatal screening test performed between 14 and 22.6 weeks of pregnancy (optimal between 16-18 weeks). It measures four biochemical markers in the maternal blood to assess the risk of chromosomal abnormalities and neural tube defects in the fetus.

Markers Measured in Quadruple Test

1. Beta-Human Chorionic Gonadotropin (β-hCG)

   • A hormone produced by the placenta.
   • Abnormally high or low levels may indicate chromosomal abnormalities.

2. Alpha-Fetoprotein (AFP)

   • A protein produced by the fetal liver.
   • High levels may suggest neural tube defects (e.g., spina bifida, anencephaly).
   • Low levels may indicate Down syndrome (Trisomy 21) or Trisomy 18.

3. Unconjugated Estriol (uE3)

   • A form of estrogen produced by the fetus and placenta.
   • Low levels may be associated with Down syndrome (Trisomy 21) and Trisomy 18.

4. Inhibin-A

   • A protein produced by the placenta.
   • Elevated levels may indicate an increased risk of Down syndrome (Trisomy 21).

Purpose of the Quadruple Test

• Screens for the following conditions:
  • Down syndrome (Trisomy 21) → Low AFP, high hCG, low uE3, high Inhibin-A
  • Trisomy 18 (Edwards syndrome) → Low AFP, low hCG, low uE3
  • Neural tube defects (e.g., spina bifida, anencephaly) → High AFP

Test Interpretation

• The results are not diagnostic but indicate the risk level.
• The risk is calculated based on:
  • Maternal age
  • Gestational age
  • Weight
  • Ethnicity
  • Diabetic status
• If results indicate high risk, further confirmatory tests like NIPT, amniocentesis, or chorionic villus sampling (CVS) may be recommended.