Pregnancy Guide
NHS Choices

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

You can have a screening test done during pregnancy to find out if your baby has Down’s syndrome, Edwards’ syndrome or Patau’s syndrome. Women who find out that their baby has a higher chance of these syndromes will be offered a further screening test or an invasive procedure. You can choose whether or not to have these tests.  Some women want to find out if their baby has one of the syndromes and some do not.

What is Down’s syndrome?

Down’s syndrome is a genetic condition caused by an extra chromosome 21 in all or some cells. A person with Down’s syndrome has 47 chromosomes instead of the usual 46.

People with Down’s syndrome are affected in different ways.  All have some lifelong learning disability.  People with Down’s syndrome will look like other people with Down’s syndrome, for instance they are often shorter than other people in their family and have almond-shaped eyes. They will also look like other people in their family.  Down’s syndrome does not usually run in families.

  • Most children with Down’s syndrome go to mainstream primary school and can lead semi-independent adult lives, but some need more support than others. People with Down’s syndrome are more likely to have heart problems, thyroid problems, hearing and sight problems. Many of these conditions can be treated.  Alzheimer’s disease (a form of dementia) may affect people with Down’s syndrome at an earlier age than other people.
  • People with Down’s syndrome who have good healthcare can live into their 60s.

Down’s syndrome happens in about 1 in 415 pregnancies in Wales.  All women have a chance of having a baby with Down’s syndrome. The chance increases with age, but babies are also born with Down’s syndrome to younger women. This is why women of all ages are offered the screening test.

What are Edwards’ syndrome and Patau’s syndrome?

Edwards’ syndrome is caused by an extra chromosome 18 in all or some cells. Patau’s syndrome is caused by an extra chromosome 13 in all or some cells.

Most babies with Edwards’ syndrome or Patau’s syndrome will die before they are born or shortly after birth. Some babies may survive to adulthood but this is rare.

Babies with Edwards’ syndrome and Patau’s syndrome have a range of problems. All babies will be affected by developmental delay and lifelong learning disability.  Children with these syndromes will take longer than usual to develop or learn.  They will need to attend special school.

Many people with Edwards’ syndrome or Patau’s syndrome can have other conditions which can be very serious, including heart problems, feeding difficulties, breathing difficulties and cleft lip and palate. They can also be prone to infections. Edwards’ syndrome and Patau’s syndrome do not usually run in families.

Edwards’ syndrome happens in 1 in 1656 pregnancies in Wales and Patau’s syndrome 1 in 4201.  All women have a chance of having a baby with Edwards’ syndrome or Patau’s syndrome. The chance increases with age, but babies are also born with these syndromes to younger women. This is why women of all ages are offered the screening test.

What will the screening test result tell me?

There are a number of screening tests for these syndromes. None of these tests show definitely whether a baby has one of these syndromes or not. They only tell you what chance you have of your baby having one of the syndromes. The tests will not be able to tell you how affected your baby might be.

The screening test does not pick up all babies with these syndromes. For example, on average, for every 10 babies with these syndromes only around seven or eight will be picked up by screening. This means two or three out of every 10 babies with these syndromes will not be picked up by the screening test.

The combined test is carried out before you are 14 weeks pregnant.  If you have the combined test you will get two different results.  One will tell you your chance of your baby having Down’s syndrome.  The other will tell you your chance of your baby having Edwards’ syndrome or Patau’s syndrome.

The quadruple test is carried out at around 16 weeks of pregnancy and will only tell you your chance of having a baby with Down’s syndrome.

What are the advantages of having screening for these syndromes?

If your baby has one of these syndromes, you will be able to make choices about your pregnancy. For example, you can decide whether to prepare for the birth of a baby with one of these syndromes or to end your pregnancy.

What are the disadvantages of having screening for these syndromes?

Having the test may make you anxious, especially if you have a result which shows you have a higher chance of having a baby with one of these syndromes. Higher chance is how we describe your result if it is between 1 in 5 and 1 in 150.  If the result is between 1 in 5 and 1 in 150, you will be offered either:

  • another screening test called non-invasive prenatal testing (NIPT), which is more accurate than the combined or quadruple test, or
  • an invasive test to see if your baby definitely has one of these syndromes.

Because the invasive test (either amniocentesis or chorionic villus sampling (CVS)), can cause a miscarriage, many women find this a difficult decision. Some women may wish they had not had the screening test because making this decision is difficult. 

Should I have the test for Down’s syndrome, Edwards’ syndrome and Patau’s syndrome?

Only you can decide whether to have the test or not. Some women want to find out if their baby has these syndromes, and some don’t. All hospitals in Wales offer women a screening test but the decision whether to have the test or not is yours. You can discuss with your midwife what you want to do. They will support you whatever you decide. 

What screening test will I be offered?

Combined screening

You will be offered an ultrasound scan, known as a nuchal translucency scan, to measure the small space at the back of the baby’s neck. You will then be offered a blood test. The measurements taken at the scan, the results of the blood test and your age are used to work out the chance of your baby having Down’s syndrome and your chance of having a baby with Edwards’ syndrome or Patau’s syndrome. This combined test is taken when you are between 11 and 14 weeks pregnant.  If you are having twins you will also be offered this test.

Sometimes it is difficult to measure the space at the back of the baby’s neck. For example, babies may be lying in the wrong position or you may be above average weight for your height and this makes looking at the baby difficult because the images are not clear. If the person performing the scan (the sonographer) cannot get a measurement, they will tell you.

Quadruple screening

You will be offered a quadruple test if the sonographer cannot get the measurement or if you go for the scan appointment later than 14 weeks pregnant.  This involves having a blood test to find out your chance of having a baby with Down’s syndrome but not Edwards’ syndrome or Patau’s syndrome. This test is not offered in Wales in twin pregnancies as it is not as accurate as in single pregnancies.  This test is taken at 15 to 18 weeks of pregnancy.

You can choose whether or not to have an early pregnancy scan. You can also choose to have an early pregnancy scan but not to have the screening test for Down’s syndrome, Edwards’ syndrome or Patau’s syndrome. 

The quadruple test is not offered in Wales after 18 weeks of pregnancy.

The scans you have in pregnancy can occasionally see things that may cause us to suspect your baby may have one of these syndromes. You may be offered an invasive test at this stage.

Where can I have the test done?

Your midwife will tell you where the test can be done. 

Results

Will my results be confidential?

The NHS keeps the results of all tests confidential.  Hospital policies vary on how many healthcare professionals have access to your test results.  Your midwife will be able to explain the local arrangements to you.

How will I get the result from my screening test?

Your midwife will tell you how and when you will get the result of the test. The results are given as either ‘higher chance’ or ‘lower chance’.

What happens if I get a lower chance result?

If the result shows you have a lower chance of having a baby with Down’s syndrome, Edwards’ syndrome or Patau’s syndrome, no more tests are offered. Please remember that having a lower chance does not mean that you have no chance of having a baby with one of these syndromes.

What if I have a higher chance result?

If your test result shows you have a higher chance of having a baby with Down’s syndrome or a higher chance of having a baby with Edwards’ syndrome or Patau’s syndrome (that is, a chance of 1 in 5 to 1 in 150), you will be offered an appointment with a midwife or doctor. They will explain your test result to you in detail, including your individual chance, and you can discuss whether or not you want to have a non-invasive prenatal test (NIPT) test or an invasive procedure. You may face some difficult decisions after an invasive procedure that you need to be aware of beforehand.

Remember that the lower the number, the higher the chance.  So, for example, 1 in 80 is a higher chance of having a baby with Down’s syndrome than 1 in 140.

NIPT tests are not available in Wales in twin pregnancies.

Between 2% and 3% of women (that is, between two and three out of 100) who have the screening test have a result which shows they have a higher chance of having a baby with one of these syndromes.

Non-invasive prenatal test (NIPT)

NIPT is a further screening test and will not give a definite result. However, it is more accurate than the combined or quadruple test.  It is a blood test taken from you in the usual way – your blood will have some of the baby’s DNA in it. The blood is sent to the laboratory and screened to look for Down’s syndrome, Edwards’ syndrome and Patau’s syndrome.

If you choose to have this test it usually takes about two weeks to get the result.  In about 2% of cases the NIPT test will not be able to give a result and you will be offered an invasive test. The NIPT result will tell you if you have a high or low chance of your baby having Down’s syndrome, Edwards’ syndrome or Patau’s syndrome.

If the NIPT result is high chance, you will be offered an invasive test to tell you for definite if your baby has one of the three syndromes. If you choose not to have an invasive test we can give you as much or as little information as you want about the syndrome that the NIPT shows a high chance for and you will be supported in your decision.

If the NIPT is low chance, it is very unlikely that your baby will have Down’s syndrome, Edwards’ syndrome or Patau’s syndrome and you will not be offered any further testing.

Invasive procedure for Down’s syndrome, Edwards’ syndrome and Patau’s syndrome

This leaflet gives some basic information about the invasive procedures you could be offered if you have the screening tests. More information is available in other leaflets and on our website.

What invasive procedures will I be offered?

Depending on how many weeks pregnant you are, you will be offered either a chorionic villus sampling (CVS) or amniocentesis procedure.

What is chorionic villus sampling (CVS)?

CVS is a procedure during which a doctor removes a small amount of tissue from your placenta (afterbirth) during your pregnancy. The cells in this tissue are tested in the laboratory to look for these three syndromes.

You can usually have CVS between 11 and 14 weeks of pregnancy. CVS involves some risk. It can cause a miscarriage in more than 1% but less than 2% of pregnancies (between 1 out of 50 and 1 out of 100 pregnancies). 

If you are having twins, the risk of miscarriage will be more than 2% and less than 3% (between 2 and 3 out of 100 pregnancies).

What is amniocentesis?

Amniocentesis is a procedure to remove about 15 to 20 millilitres (that is, three to four teaspoons) of amniotic fluid from around the baby in the womb. The cells from your baby that are floating in this fluid can be tested in the laboratory to look for these three syndromes.

It can be done after you are 15 weeks pregnant.

Amniocentesis involves some risk. It causes a miscarriage in around 1% of pregnancies (1 in every 100 pregnancies).  If you are having twins the risk of miscarriage will be around 2%.

What would an invasive test result tell me?

The result would tell you if your baby has one of these syndromes. If they do, you can decide whether to prepare for the birth of your baby or to end your pregnancy.

More information

You can get information about screening for Down’s, Edwards’ and Patau’s syndromes from your midwife or your hospital doctor (your obstetrician) or from www.antenatalscreening.wales.nhs.uk.

Other sources of information are listed below.

Antenatal Results and Choices (ARC)

Down’s Syndrome Association (DSA)

Support Organisation for Trisomy 13/18 (Edwards’ and Patau’s syndromes) (SOFT UK)

  • Phone: 0330 088 1386
  • Email: enquiries@soft.org.uk
  • Website: www.soft.org.uk

Private tests

The quality of the screening offered by the NHS in Wales is monitored. Some women pay privately to have screening tests.  Screening done by private clinics is not monitored by the NHS.  This means that your midwife will have no information about the quality and accuracy of any screening tests carried out by private clinics.

Film clip

There is a film clip available to give you more information about screening for Down’s syndrome, Edwards’ syndrome and Patau’s syndrome.  You can watch this before you see your midwife for the first time. The film clip is available from www.antenatalscreening.wales.nhs.uk/public/home. At the end of the clip there are some questions (see below) that you may want to consider before you have your first appointment with your midwife.

  • Do I know enough about Down’s syndrome, Edwards’ syndrome and Patau’s syndrome in order to make decisions about whether I would want testing for these conditions?
  • Do I know how to find out more information if I want it?
  • How important it is for me to know whether my baby has Down’s syndrome, Edwards’ syndrome or Patau’s syndrome before it is born, and would I be prepared to have an invasive test that has around a 1% risk of miscarriage to find this out?
  • Would I continue with the pregnancy if the baby had Down’s syndrome, Edwards’ syndrome or Patau’s syndrome? Would I need more information about the support available in this instance?
  • Would I consider ending the pregnancy for any of these conditions?
  • If I take the combined or quadruple test alone, would only knowing my chance of having a baby with one of these conditions be enough for me?
  • If I had a higher chance result from the combined or quadruple test which choice would I make?
  • Would I be happy to have no other tests if the NIPT was low chance?

 

 


Last Updated: 08/11/2017 13:27:16