Quadruple Test: Complete Guide
The quadruple test (sometimes called the "quad test") is a blood-based screening test offered later in pregnancy to women who missed the combined test window. It's a useful backup option, but it's important to understand how it differs from earlier screening so you know what your results can and can't tell you.
What the quadruple test measures
The test analyses a single blood sample for four substances:
- AFP (alpha-fetoprotein) — a protein made by the baby, can flag neural tube defects when raised
- hCG (human chorionic gonadotropin) — the pregnancy hormone
- Unconjugated oestriol — an oestrogen produced by the placenta and baby
- Inhibin-A — a hormone from the placenta
Your levels are combined with your age, weight, and gestational age to produce a risk score for conditions such as Down's syndrome (trisomy 21), Edwards' syndrome (trisomy 18), and neural tube defects like spina bifida.
Who is offered it, and when
The quadruple test is offered between roughly 14 and 20 weeks, usually to women who:
- Missed the combined test window (which needs to happen between 11 and 14 weeks)
- Booked their pregnancy later than usual
- Have a nuchal translucency measurement that couldn't be taken (for example, if the baby's position made it hard to see)
Because it doesn't include the nuchal translucency ultrasound measurement or PAPP-A blood marker used in the combined test, it's a slightly less precise screening tool — but it's still a valid, NHS-recommended option and far better than having no screening at all.
Understanding your result
Like the combined test, this is a screening test, not a diagnosis. You'll be given a risk score (for example, "1 in 500") rather than a yes/no answer.
- A lower-risk result means the chance of the condition is small, but it doesn't rule it out completely
- A higher-risk result means you'll be offered a discussion with a midwife or specialist about further diagnostic testing, such as amniocentesis or NIPT, to get a definitive answer
- Screening results alone are never used to diagnose a condition — only invasive or NIPT testing can do that
Your midwife will talk you through what your specific numbers mean and what your options are if the result comes back higher risk.
Frequently Asked Questions
When is the quadruple test done?
It's usually carried out between 14 and 20 weeks of pregnancy. It's typically offered to women who missed the combined screening test, which has to be done between 11 and 14 weeks, or whose nuchal translucency measurement wasn't obtainable during that window.
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. The quadruple test relies on blood markers alone, so it's slightly less precise, but it remains a recognised, worthwhile screening option and is far better than skipping screening altogether.
What happens if my quadruple test result comes back higher risk?
You'll be offered an appointment with a midwife or specialist to talk through your result and further testing options, such as NIPT (a more detailed blood test) or a diagnostic test like amniocentesis. These follow-up tests can give a much clearer, more definitive answer than screening alone.
This article is for informational purposes only and does not constitute medical advice.
Related articles: