Quad Screen Test — Prenatal Genetic Screening
Written & medically reviewed by Dr. Shaivalini Kamarapu
MBBS · MS (Obstetrics & Gynaecology) · Fellowship in Reproductive Medicine · 20+ years of clinical experience
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What is a quad screen test?
The quad screen, also known as the quadruple marker test, second trimester screen, or simply the quad test, is a prenatal screening test performed during the second trimester of pregnancy to check for certain birth defects and chromosomal conditions.
The test combines the mother's age with the levels of four substances measured in a blood sample: beta-human chorionic gonadotrophin (β-hCG), unconjugated estriol, alpha-fetoprotein (AFP), and inhibin A.
Screening
2nd trimester
What does the quad screen measure?
Beta-human chorionic gonadotrophin
A hormone made by the placenta during pregnancy.
Unconjugated estriol
A hormone produced by the placenta and the baby's liver.
Alpha-fetoprotein
A protein produced by the developing baby.
Inhibin A
A hormone produced by the placenta.
When is the quad screen offered?
The combined screening test is generally offered between 11 and 14 weeks of pregnancy.
If you book too late for the combined screening test, the quadruple test may be offered instead.
The quad test may also be offered when the baby's position makes it difficult or impossible to measure the nuchal translucency during the first-trimester scan.
Having the test is your choice. Some parents prefer to know the chance of their baby being affected by a condition so they can prepare for future decisions, while others may choose not to have screening.
What are the risks?
Non-invasive screening
The quad test is performed using a blood sample and does not involve an invasive procedure.
No procedural miscarriage risk
Because it is a blood-based screening test, it does not carry the miscarriage risk associated with invasive prenatal diagnostic procedures.
Waiting for results
Although the test itself is simple, waiting for screening results can sometimes be an anxious period for expectant parents.
How accurate is the quad screen?
Down syndrome detection
Around 80%
The quadruple test can identify around 80 out of 100 babies who have Down syndrome.
Compared with combined screening
Less accurate
The quadruple test is recognised as slightly less accurate than the combined first-trimester screening test.
How to interpret the results
The quad screen does not tell you for certain whether your baby has a condition. Instead, it provides an estimated chance, which may be classified as higher chance or lower chance.
Higher chance
1 in 150 or less
A result of 1 in 150 or a number lower than 150, such as 1 in 100, is considered a higher-chance screening result.
Lower chance
More than 1 in 150
A result above the cut-off, such as 1 in 200, is considered a lower-chance screening result.
How is the quad screen done?
The quadruple test is performed with a simple blood test.
A healthcare professional takes a blood sample from a vein in your arm.
The sample is sent to a laboratory for analysis.
The time taken to receive results can vary depending on the laboratory and location.