What Is the Quad Screen Test?
The quad screen, also known as the quadruple marker screen, is a second-trimester prenatal screening test that assesses your baby's risk for certain birth defects and chromosomal abnormalities. This test measures four specific substances in your blood and is usually performed between 15 and 20 weeks of pregnancy.
What Does the Quad Screen Measure?
The quad screen analyzes the levels of these four substances:- Alpha-fetoprotein (AFP): A protein made by the baby's liver. High levels may indicate neural tube defects like spina bifida.
- Human chorionic gonadotropin (hCG): A hormone produced by the placenta. Abnormal levels can signal chromosomal issues.
- Estriol: An estrogen produced by the baby and placenta.
- Inhibin A: A hormone released by the placenta that helps detect Down syndrome risks.
What Can the Quad Screen Detect?
The quad screen does not diagnose conditions but provides an assessment of risks. It helps screen for:- Neural tube defects (e.g., spina bifida)
- Down syndrome (trisomy 21)
- Trisomy 18 (a severe genetic condition)
- Other developmental or chromosomal abnormalities
How Accurate Is the Quad Screen?
While helpful, the quad screen is not 100% accurate. It has a detection rate of about 80% for Down syndrome and 75-80% for spina bifida. False positives can happen, which may lead to additional testing, such as an amniocentesis or a detailed ultrasound.
Should You Get the Quad Screen?
The quad screen is optional but is often recommended if:- You are 35 or older, which increases the risk of chromosomal abnormalities.
- You have a family history of birth defects.
- You had abnormal results from first-trimester screenings.
The quad screen is a valuable second-trimester screening tool that helps assess risks for certain birth defects and chromosomal abnormalities. While it doesn’t provide a diagnosis, it can guide you and your doctor in determining if further testing is needed.
