Quadruple Marker- Second Trimester

Key Components & Purpose

The test measures the following substances in the mother's blood, which are combined with maternal age, weight, and ethnicity to determine risk:

• Alpha-fetoprotein (AFP): A protein made by the baby.
• Human Chorionic Gonadotropin (hCG): A hormone produced by the placenta.
• Estriol (uE3): A form of estrogen produced by the baby and placenta.
• Inhibin-A: A protein produced by the placenta.

What Results Indicate

• High Risk: A "positive" result does not mean the baby has a defect, but that the risk is higher, requiring further tests (e.g., ultrasound, amniocentesis).
• Low Risk: A "negative" or "low-risk" result indicates a low probability of these conditions.
• Common Use Cases: Often recommended for women over 35, Those with a family history of birth defects, or those who missed the first-trimester screening.

Accuracy & Considerations

The quad screen has a reported accuracy of roughly 82% for trisomy 21 and is a safe, routine test that poses no risk of miscarriage. It is primarily a screening tool rather than a diagnostic one.

Commonly Screened Conditions

• Down Syndrome (Trisomy 21): Often associated with higher hCG and Inhibin-A, and lower AFP and Estriol.
• Edwards Syndrome (Trisomy 18): Usually, all four markers are low.
• Neural Tube Defects: High levels of AFP may indicate defects like spina bifida.