[Skip to content]

.

Screening for Down's, Edward's and Patau's Syndrome.

Choosing whether to have screening for Down's, Edward's and Patau's Syndrome is an important decision, for you and for your baby. 

Your midwife will talk to you about the tests available to you on the NHS at your booking appointment, as the type of test we can offer you will vary according to the stage of your pregnancy at the time of testing.

This section will give you some information about screening tests available to help you decide whether to be screened.   

There is some really useful information on NHS Choices about Down Syndrome which we suggest you read.


Screening for Down's Edward's and Patau's Syndrome is offered to pregnant women of all ages. The tests can provide information about the chance of a baby with any of these conditions.  These tests use blood samples taken from the mother, measurements taken from ultrasound scans or both to work out this chance. The tests you will be offered depend on how many weeks pregnant you are.

NHS Screening in early pregnancy
The NHS combined test uses the results of a blood test and an ultrasound scan to calculate the chance of your unborn baby having Down and Edwards/Patau's Syndrome. The ultrasound scan will need to be performed between 11 weeks and 2 days to 14 weeks and 1 day of pregnancy. This scan measures the amount of fluid lying under the skin at the back of the baby’s neck. This is called the nuchal translucency (NT) measurement. A blood sample is also taken from the mother at the time of the scan and is used to measure the amount of some substances that are found naturally in the mother’s blood. 

The sample is then sent off to the laboratory alongside all of the scan details and a computer program then uses the results from the blood sample combined with the NT measurement to work out a chance figure. In addition to the results from the blood sample and the NT measurement, the program also uses the mother’s age, weight, weeks of pregnancy, family origin and smoking details to work out this risk (chance) figure.

Screening later in pregnancy
If it has not been possible to have the combined test in early pregnancy, you will be offered a blood test on the NHS between 14 weeks and 2 days to 20 weeks of pregnancy.  This test will be for Down's syndrome only.  It analyses different substances to those measured in early pregnancy. This test is known as the quad (or quadruple) test. 

It is important to remember that if you would like a screening test for any of these conditions this can only be done up to 20 weeks of pregnancy.  If you are experiencing problems arranging an appointment to have this test, please contact either your community midwife or the maternity hospital where you plan to have your baby.

Results from Down and Edward's/Patau's Syndrome screening
Regardless of which NHS screening test you choose to have have you should see your midwife within two weeks of the test being taken to get your results.  You will also a receive a results letter in the post.

At this appointment you will be given your chance result - for example 1:250 (1 in 250).  This result would be classed as a "low chance" screening result as all results below 1:150 are classed as "low chance".  Another way to understand this result, is that as the second number in the result gets bigger, the chance of your baby having Down’s or Edward's/Patau's syndrome gets smaller.

If you have chosen to have screening for Down's, Edward's and Patau's syndrome you will receive two chance results.  One for Down's syndrome and a combined chance for Patau's/Edward's syndrome.

It is important to remember with any screening test that "low chance" does not mean "no chance" but the chances of having an affected baby are very small.  

High chance results from NHS screening
National guidelines suggest that results from Down or Edward's/Patau's Syndrome screening that are higher than 1:150 are classed as "high chance". 

If you get a high chance result from a screening test it means that we will offer you more tests. It does not mean that your baby definitely has one of these conditions. 

In Leicestershire you will be contacted by an antenatal midwife, usually by telephone and invited into the maternity hospital where you plan to have your baby to discuss your result and what options there are for further tests.  Your options following a high chance NHS screening test result are:

  1. Have no further testing for Down's, Edward's or Pataus' syndrome

  2. Have non-invasive prenatal testing (NIPT). NIPT is more accurate than the combined or quadruple test, though it is not quite as accurate in twin pregnancies. It works by measuring DNA (genetic material) in your blood. Some of this DNA will be from the baby’s placenta. If there is more DNA than expected from chromosomes 21, 18 or 13 it may mean that your baby has Down’s syndrome, Edwards’ syndrome or Patau’s syndrome. Like every screening test, though, it does not give a definite answer. NIPT cannot harm your baby. Most women will get their result within 2 weeks.

    1. Most people will get a lower-chance result, meaning your chance of having a baby with the condition is low. You will not be offered a diagnostic test.
    2. If your NIPT result shows a higher-chance result then the chance of your baby having the condition is high. You will then be offered a diagnostic test, though it is up to you whether or not to have this. In a small number of cases, NIPT might produce no result. You can then choose between one further NIPT, a diagnostic test or no further testing.

 

  1.  Have a diagnostic test which can tell you definitely whether your baby has Down's, Edward's or Patau's Syndrome or not.

    1. There are two diagnostic tests available – chorionic villus sampling (CVS) and amniocentesis. These tests are explained in more detail, on the diagnostic testing for Down's, Edward's and Patau's Syndrome page of this website.  Both of these tests will be able to tell you if your baby is affected with a chromosomal problem but both tests have an associated risk of miscarriage in about 0.5% of cases as a direct result of having the test.  You should also be aware that having a diagnostic test will look at more than just the chromosomes relating to these conditions and so we may find something that we were not expecting but this is very unlikely.

Your midwife or doctor will give you as much information and support as you need at this time, because we appreciate that this can be a difficult decision to make. You will be given time to make up your mind about what to do next.

In summary you have three options following a high chance NHS screening test.

  1. You can decide not to have any further tests.

  2. You can have NIPT which is a more accurate screening test than the combined or quadruple test but it does not give a definitive answer.

  3. You can have a diagnostic test to find out if your baby is affected with Down Syndrome, knowing that this will slightly increase the risk of miscarriage.

Screening is your choice. You do not have to have the screening test. Some people want to find out if their baby has one of the conditions and some do not. Screening is not perfect and might provide an incorrect result. It may lead to personal choices about your pregnancy.

Down syndrome information on NHS Choices website

Translate this site in to:
powered by
Google Translate