Screening
Combined Screening Test
The combined test uses a blood test and the nuchal translucency ultrasound measurement to estimate the chance of Down’s and other chromosomal syndromes in early pregnancy.
Quick answer
Combined Screening Test: what it is and what the results mean
The combined screening test brings together a blood test measuring pregnancy hormones and an ultrasound measurement of the fluid at the back of the baby’s neck (nuchal translucency), along with the mother’s age and pregnancy details.
- Why it is done: It is offered in early pregnancy to estimate the chance of Down’s syndrome (trisomy 21) and, in many programmes, Edwards’ and Patau’s syndromes, helping parents decide whether to have further tests.
- Understanding results: The result is a chance (for example 1 in 1,000), not a diagnosis.
What it is
The combined screening test brings together a blood test measuring pregnancy hormones and an ultrasound measurement of the fluid at the back of the baby’s neck (nuchal translucency), along with the mother’s age and pregnancy details.
Why it is done
It is offered in early pregnancy to estimate the chance of Down’s syndrome (trisomy 21) and, in many programmes, Edwards’ and Patau’s syndromes, helping parents decide whether to have further tests.
What to expect
It involves a blood test and an ultrasound scan, usually between about 11 and 14 weeks. The results are combined to give an estimated chance for each condition.
Understanding the results
The result is a chance (for example 1 in 1,000), not a diagnosis. A lower-chance result is reassuring; a higher-chance result offers the option of more accurate screening (NIPT) or a diagnostic test.
Good to know
Risks and limitations
The test is safe and carries no risk to the pregnancy, but it is a screening estimate and can be falsely reassuring or falsely high. It must be done within a specific time window to be valid.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
Combined Screening Test: frequently asked questions
What does a “1 in 1,000” result mean?
It means that out of 1,000 pregnancies with the same result, one would be expected to have the condition and 999 would not. It is an estimate of chance, not a diagnosis.
What happens after a higher-chance result?
You are offered further options, which may include the more accurate NIPT blood test or a diagnostic test such as amniocentesis or CVS to confirm. The choice is entirely yours.
Related tests
Other screening investigations
Sources
Where this is drawn from
- NHS — Screening and pregnancy
- NICE — antenatal and screening guidance
- UK National Screening Committee
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