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Screening for Down's syndrome, Edwards' syndrome and Patau's syndrome

You will be offered a screening test for Down's syndrome, Edwards' syndrome and Patau's syndrome between 10 and 14 weeks of pregnancy. This is to assess your chances of having a baby with one of these conditions.

Down's syndrome is also called trisomy 21 or T21. Edwards' syndrome is also called trisomy 18 or T18, and Patau's syndrome is also called trisomy 13 or T13.

If a screening test shows that you have a higher chance of having a baby with Down's syndrome, Edwards' syndrome or Patau's syndrome, you'll be offered further tests to find out for certain if your baby has the condition.

Important: Coronavirus (COVID-19) update

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What are Down's syndrome, Edwards' syndrome and Patau's syndrome?

Down's syndrome

Down's syndrome causes some level of learning disability.

People with Down's syndrome may be more likely to have other health conditions, such as heart conditions, and problems with the digestive system, hearing and vision. Sometimes these can be serious, but many can be treated.

Read more about Down's syndrome

Edwards' syndrome and Patau's syndrome

Sadly, most babies with Edwards' syndrome or Patau's syndrome will die before or shortly after birth. Some babies may survive to adulthood, but this is rare.

All babies born with Edwards' syndrome or Patau's syndrome will have a wide range of problems, which can be very serious. These may include major complications affecting their brain.

Read more about Edwards' syndrome and Patau's syndrome.

What does screening for Down's syndrome, Edwards' syndrome and Patau's syndrome involve?

Combined test

A screening test for Down's syndrome, Edwards' syndrome and Patau's syndrome is available between weeks 10 and 14 of pregnancy. It's called the combined test because it combines an ultrasound scan with a blood test. The blood test can be carried out at the same time as the 12-week scan.

If you choose to have the test, you will have a blood sample taken. At the scan, the fluid at the back of the baby's neck is measured to determine the "nuchal translucency". Your age and the information from these 2 tests are used to work out the chance of the baby having Down's syndrome, Edwards' syndrome or Patau's syndrome.

Obtaining a nuchal translucency measurement depends on the position of the baby and is not always possible. If this is the case, you will be offered a different blood screening test, called the quadruple test, when you're 14 to 20 weeks pregnant.

Quadruple blood screening test

If it was not possible to obtain a nuchal translucency measurement, or you're more than 14 weeks into your pregnancy, you'll be offered a test called the quadruple blood screening test between 14 and 20 weeks of pregnancy. This only screens for Down's syndrome and is not as accurate as the combined test.

20-week screening scan

For Edwards' syndrome and Patau's syndrome, if you are too far into your pregnancy to have the combined test, you'll be offered a 20-week screening scan. This looks for physical conditions, including Edwards' syndrome and Patau's syndrome.

Can this screening test harm me or my baby?

The screening test cannot harm you or the baby, but it's important to consider carefully whether to have this test.

It cannot tell you for certain whether the baby does or does not have Down's syndrome, Edward's syndrome or Patau's syndrome, but it can provide information that may lead to further important decisions. For example, you may be offered diagnostic tests that can tell you for certain whether the baby has these conditions, but these tests have a risk of miscarriage.

Do I need to have screening for Down's syndrome, Edwards' syndrome and Patau's syndrome?

You do not need to have this screening test – it's your choice. Some people want to find out the chance of their baby having these conditions while others do not.

You can choose to have screening for:

  • all 3 conditions
  • Down's syndrome only
  • Edwards' syndrome and Patau's syndrome only
  • none of the conditions

What if I decide not to have this test?

If you choose not to have the screening test for Down's syndrome, Edwards' syndrome or Patau's syndrome, you can still choose to have other tests, such as a 12-week scan.

If you choose not to have the screening test for these conditions, it's important to understand that if you have a scan at any point during your pregnancy, it could pick up physical conditions.

The person scanning you will always tell you if any conditions are found.

Getting your results

The screening test will not tell you whether your baby does or does not have Down's, Edwards' or Patau's syndromes – it will tell you if you have a higher or lower chance of having a baby with one of these conditions.

If you have screening for all 3 conditions, you will receive 2 results: 1 for your chance of having a baby with Down's syndrome, and 1 for your joint chance of having a baby with Edwards' syndrome or Patau's syndrome.

If your screening test returns a lower-chance result, you should be told within 2 weeks. If it shows a higher chance, you should be told within 3 working days of the result being available.

This may take a little longer if your test is sent to another hospital. It may be worth asking the midwife what happens in your area and when you can expect to get your results.

You will be offered an appointment to discuss the test results and the options you have.

The charity Antenatal Results and Choices (ARC) offers lots of information about screening results and your options if you get a higher-chance result.

Possible results

Lower-chance result

If the screening test shows that the chance of having a baby with Down's syndrome, Edwards' syndrome and Patau's syndrome is lower than 1 in 150, this is a lower-chance result. More than 95 out of 100 screening test results will be lower chance.

A lower-chance result does not mean there's no chance at all of the baby having Down's syndrome, Edwards' syndrome or Patau's syndrome.

Higher-chance result

If the screening test shows that the chance of the baby having Down's syndrome, Edwards' syndrome or Patau's syndrome is higher than 1 in 150 – that is, anywhere between 1 in 2 and 1 in 150 – this is called a higher-chance result.

Fewer than 1 in 20 results will be higher chance. This means that out of 100 pregnancies screened for Down's syndrome, Edwards' syndrome and Patau's syndrome, fewer than 5 will have a higher-chance result.

A higher-chance result does not mean the baby definitely has Down's syndrome, Edwards' syndrome or Patau's syndrome.

Will I need further tests?

If you have a lower-chance result, you will not be offered a further test.

If you have a higher-chance result, you can decide to:

  • not have any further testing
  • have a second screening test called non-invasive prenatal testing (NIPT) – this is a blood test, which can give you a more accurate screening result and help you to decide whether to have a diagnostic test or not
  • have a diagnostic test, such as amniocentesis or chorionic villus sampling (CVS) straight away – this will tell you for certain whether or not your baby has Down's syndrome, Edwards' syndrome or Patau's syndrome, but in rare cases can cause a miscarriage

You can decide to have NIPT for:

  • all 3 conditions
  • Down’s syndrome only
  • Edwards’ syndrome and Patau’s syndrome only

You can also decide to have a diagnostic test after NIPT.

NIPT is completely safe and will not harm your baby.

Discuss with your healthcare professional which tests are right for you.

Whatever results you get from any of the screening or diagnostic tests, you will get care and support to help you to decide what to do next.

If you find out your unborn baby has Down's syndrome, Edwards' syndrome or Patau's syndrome

If you find out your baby has Down's syndrome, Edwards' syndrome or Patau's syndrome a specialist doctor (obstetrician) or midwife will talk to you about your options .

You can read more about what happens if antenatal screening tests find something.

You may decide to continue with the pregnancy and prepare for your child with the condition.

Or you may decide that you do not want to continue with the pregnancy and have a termination.

If you are faced with this choice, you will get support from health professionals to help you make your decision.

For more information see Public Health England: Screening tests for you and your baby.

The charity Antenatal Results and Choices (ARC) runs a helpline from Monday to Friday, 10am to 5.30pm on 020 7137 7486.

The Down's Syndrome Association also has useful information on screening.

The charity SOFT UK offers information and support through diagnosis, bereavement, pregnancy decisions and caring for all UK families affected by Edwards' syndrome (T18) or Patau's syndrome (T13).

Page last reviewed: 19 April 2021
Next review due: 19 April 2024