- First-trimester screening assesses the chance of your baby having Down's, Edwards' or Patau's syndromes.
- The standard NHS offer between 11 and 14 weeks is the 'combined test', which involves an ultrasound and a blood test.
- Non-invasive prenatal testing (NIPT) is a more accurate blood test available privately or via the NHS after a higher-risk combined test result.
- Screening tests give you a risk score, not a diagnosis. Diagnostic tests like CVS or amniocentesis are offered for a definitive answer.
What is First-Trimester Screening?
First-trimester screening is a set of tests offered to all pregnant women in the UK between weeks 11 and 14 of pregnancy. Its main purpose is to assess the chance of your baby having certain chromosomal conditions, specifically Down's syndrome, Edwards' syndrome, and Patau's syndrome. It is an optional but routine part of NHS antenatal care.
These tests do not diagnose a condition; they calculate a risk or chance. This result helps you decide whether you want to proceed with further, more invasive, diagnostic testing.
The NHS Combined Test Explained
The screening routinely offered on the NHS is called the 'combined test'. It combines information from two different sources to generate your personal risk score. The first part is a blood test, taken from your arm, which measures the levels of two pregnancy-related proteins.
The second part is an ultrasound scan, often known as the '12-week scan'. During this scan, the sonographer performs a nuchal translucency (NT) measurement, which is the thickness of the fluid at the back of the baby's neck. This measurement, along with your blood test results and your age, are combined to calculate the result.
Non-Invasive Prenatal Testing (NIPT)
NIPT is a more advanced type of screening test. It works by analysing small fragments of the baby's DNA that have crossed into the mother's bloodstream. It is more accurate at detecting Down's syndrome than the combined test and has a lower false-positive rate.
In the UK, you can pay for NIPT privately from around 10 weeks of pregnancy. The NHS will also offer you NIPT if your combined test comes back with a higher-risk result (usually defined as a chance of more than 1 in 150). This helps to reduce the number of women who go on to have unnecessary invasive tests.
Understanding Your Results
Your result will be given as either 'lower risk' or 'higher risk'. A lower-risk result means it is unlikely your baby has the condition, and you will not be offered further tests. A higher-risk result means there is an increased chance, and you will be offered a consultation with a specialist midwife or doctor.
They will discuss what the result means and talk you through the next steps, which could be to have NIPT (if you haven't already) or a diagnostic test like CVS or amniocentesis. These tests carry a small risk of miscarriage but give a definitive 'yes' or 'no' answer. The decision is always yours.
Frequently asked questions
Is first-trimester screening compulsory?
No, all antenatal screening is optional. Your midwife will discuss the tests with you, and it is your choice whether to have them. Some women want as much information as possible, while others prefer not to know.
What does a 'higher-risk' result mean?
A higher-risk result does not mean your baby has a condition. It means there is a greater chance, and you will be offered further, more definitive diagnostic tests, such as chorionic villus sampling (CVS) or amniocentesis, to get a clear yes or no answer.
Is NIPT better than the NHS combined test?
NIPT is a more accurate screening test than the combined test, with a lower 'false positive' rate. This is why the NHS now offers NIPT to women who have received a higher-risk result from their combined test, to reduce the number of women needing invasive diagnostic tests. Many women travelling from the UK or elsewhere opt for private NIPT from 10 weeks for earlier reassurance.
When will I get the results?
The results of the combined test are usually available within two weeks. Your hospital will contact you, often by letter if the result is lower-risk, or by phone if it is higher-risk.
Could a doctor-led plan help you?
A 30-minute video consultation with Dr Berra Önsoy — reviewing your case and giving you a clear, personalised next step.
Request a video consultation