Quadruple Test in Pregnancy: Complete Guide
If you missed the window for the combined screening test in early pregnancy, or booked your antenatal care later than usual, the quadruple test offers a second opportunity to screen for certain conditions. This guide explains when it's offered, what it involves, and how it compares to earlier screening options.
What the quadruple test is for
The quadruple test (sometimes called the "quad test") is a maternal blood test used to screen for the chance of your baby having Down's syndrome (trisomy 21), as well as certain physical conditions such as neural tube defects like spina bifida. It's typically offered to women who present for antenatal care too late for the combined test, or whose dating means the combined test window has already passed.
When it's offered
The quadruple test is usually carried out between 15 and 20 weeks of pregnancy, which is later than the combined test (offered between roughly 10 and 14 weeks). This later window is one reason it exists as a fallback — some women don't book their booking appointment or attend their dating scan early enough to have the combined test, and the quadruple test allows screening to still take place.
What the test measures
The quadruple test analyses levels of four substances in your blood:
- AFP (alpha-fetoprotein): a protein produced by the developing baby.
- hCG (human chorionic gonadotropin): the pregnancy hormone.
- Unconjugated oestriol: a hormone produced by the placenta and baby.
- Inhibin-A: a hormone produced by the placenta.
These levels, combined with your age and the pregnancy's gestation, are used to calculate a personalised chance (not a diagnosis) of the baby having Down's syndrome or a neural tube defect.
How it compares to the combined test
The combined test, which uses blood markers plus the nuchal translucency measurement from an ultrasound, is generally considered more accurate, detecting a higher proportion of pregnancies affected by Down's syndrome. The quadruple test is a blood test only — there's no ultrasound measurement involved — so it's somewhat less precise, but it remains a valuable and NHS-recommended option when the earlier window has been missed. It's still a genuinely useful screening tool, not a lesser or unnecessary alternative.
What happens next
If your result comes back as higher-chance, your midwife or a specialist will talk you through further options, which may include non-invasive prenatal testing (NIPT) for a more detailed risk assessment, or a diagnostic test such as amniocentesis if you want a definitive answer. You're never obliged to proceed with further testing — the choice is entirely yours, and support is available whichever path you choose.
Frequently Asked Questions
When is the quadruple test carried out?
It's usually done between 15 and 20 weeks of pregnancy. It's typically offered to women who missed the combined test window (roughly 10 to 14 weeks) because they booked antenatal care later or presented too late in the pregnancy for the earlier test.
Is the quadruple test as accurate as the combined test?
The combined test is generally considered more accurate because it includes an ultrasound measurement alongside blood markers, whereas the quadruple test relies on blood results alone. That said, the quadruple test is still a recognised, valuable NHS screening option and gives useful information when the earlier test has been missed.
What happens if my quadruple test result comes back higher-chance?
You'll be offered a conversation with your midwife or a specialist to discuss your options, which usually include further non-invasive testing (NIPT) or a diagnostic test such as amniocentesis for a definitive answer. A higher-chance result is not a diagnosis — it simply means further testing can give you more clarity if you choose to pursue it.
This article is for informational purposes only and does not constitute medical advice.
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