Your pregnancy and baby guide

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

All pregnant women in England are 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 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, Edwards' or Patau's syndromes, you'll be offered diagnostic tests to find out for certain if your baby has the condition.

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

Down's syndrome

Down's syndrome causes some level of learning disability. It can vary from mild to severe.

Some health problems are more common in people with Down's syndrome, 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' and Patau's syndromes

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

All babies born with Edwards' or Patau's syndromes will have a wide range of problems, which are usually very serious. These may include major brain abnormalities.

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

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

Combined test

A screening test for Down's, Edwards' and Patau's syndromes 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 scan can be carried out at the same time as the pregnancy dating 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 two tests is used to work out the chance of the baby having Down's, Edwards' or Patau's syndromes.

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 wasn't 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 quite as accurate as the combined test.

Mid-pregnancy scan

For Edwards' and Patau's syndromes, if you are too far into your pregnancy to have the combined test, you'll be offered a mid-pregnancy scan. This looks for physical abnormalities and 11 rare conditions, including Edwards' and Patau's syndromes.

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 doesn't have Down's, Edward's or Patau's syndromes, 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, Edwards' and Patau's syndromes?

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 don't.

You can choose to have screening for:

  • all 3 conditions
  • Down's syndrome only
  • Edwards' and Patau's syndromes 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, Edwards' or Patau's syndromes, you can still choose to have other tests, such as a dating 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 abnormalities.

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

Getting your results

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

If you have screening for all of them, you will receive two results: one for your chance of having a baby with Down's syndrome, and one for your combined chance of having a baby with Edwards' or Patau's syndromes.

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. 

You can read about people's experiences of deciding to continue a pregnancy on the ARC website.

Possible results

Lower-chance result

If the screening test shows that the chance of having a baby with Down's, Edwards' and Patau's syndromes 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, Edwards' or Patau's syndromes.

Higher-chance result

If the screening test shows that the chance of the baby having Down's, Edwards' or Patau's syndromes 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 women accepting screening for Down's, Edwards' and Patau's syndromes, fewer than 5 will have a higher-chance result.

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

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 will be offered a diagnostic test, such as amniocentesis or chorionic villus sampling (CVS). This will tell you for certain whether or not the baby has Down's, Edwards' or Patau's syndrome.

About 0.5 to 1 in 100 diagnostic tests (0.5 to 1%) result in a miscarriage. It's up to you whether to have the further tests.

When trying to decide whether to have a diagnostic test, try to weigh up the risk of miscarriage with how important the result will be to you.

Chorionic villus sampling (CVS)

This diagnostic test is usually done between weeks 11 and 14 of pregnancy. A fine needle, usually inserted through the mother's tummy (abdomen), is used to take a tiny sample of tissue from the placenta. The cells from the tissue are then tested for Down's, Edwards' or Patau's syndromes.

Read more about CVS.

Amniocentesis

Amniocentesis is done from around week 15 of pregnancy. A fine needle is passed through the mother's tummy into the uterus to collect a small sample of the fluid surrounding the baby. The fluid contains cells from the baby, which are tested for Down's, Edwards' or Patau's syndromes.

Read more about amniocentesis.

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

A small number of women who have a diagnostic test will find out their baby has Down's, Edwards' or Patau's syndrome. They then have two options.

Some women decide to continue with the pregnancy and prepare for their child with the condition, and others decide they do not want to continue with the pregnancy and have a termination (abortion).

If you are faced with this choice, you will get support from health professionals to help you make your decision. You can get more information from the charity Antenatal Results and Choices (ARC), which runs a helpline from Monday to Friday on 0845 077 2290 or 020 7137 7486 from a mobile.

The Down's Syndrome Association also has useful information on screening, and the UK National Screening Committee has produced a booklet called Screening tests for you and your baby.

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).

Media last reviewed: 27/02/2017

Media review due: 27/02/2020

Page last reviewed: 22/02/2018
Next review due: 22/02/2021