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.

You are advised to watch a film clip before you see your midwife for the first time. The film clip, which gives you more information about screening for these syndromes, is available from:  http://www.antenatalscreening.wales.nhs.uk/public/home

What is Down’s syndrome?

Down’s syndrome is caused by an extra copy of chromosome 21 in all or some cells of the body.

People with Down’s syndrome can have a good quality of life and most say they enjoy their lives. With support, many people with Down’s syndrome are able to get jobs, have relationships and live semi independently in adulthood.

A person with Down’s syndrome will have some level of learning disability. This means they will find it harder than most people to understand and to learn new things. They may have communication challenges and difficulty managing some everyday tasks. Most children with Down’s syndrome attend mainstream schools but require additional support.

People with Down’s syndrome are more likely to have some medical conditions, including heart conditions and leukaemia. Many of these conditions can be treated, with good outcomes. 

In Wales, 90% (9 out of 10) children with Down’s syndrome live past their fifth birthday.  For babies without serious health problems, survival rates are similar to that of other children.  With good health care, most people will 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.

You can get more information about Down’s syndrome and living with people with Down’s syndrome from the Down’s Syndrome Association at www.downs-syndrome.org.uk.

What are Edwards’ syndrome and Patau’s syndrome?

Babies with Edwards’ syndrome have an extra copy of chromosome 18 in all or some cells. Babies with Patau’s syndrome have an extra copy of chromosome 13 in all or some cells.

Sadly the survival rates are low and, of those babies born alive in Wales, only around 13% (1 out of 7) live past their first birthday. Some babies may survive to adulthood but this is rare.

All babies born with Edwards’ syndrome and Patau’s syndrome will have a learning disability and a wide range of physical challenges, which can be extremely serious. They may have problems with their heart, limbs, kidneys and digestive system. Around half of babies with Patau’s syndrome will have a cleft lip and palate. Babies with Edwards’ syndrome and Patau’s syndrome will have a low birthweight.

Despite their difficulties, children can slowly make progress in their development. Older children with either condition would need to attend a specialist school.

Edwards’ syndrome happens in 1 in 1656 pregnancies in Wales and Patau’s syndrome in 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.

You can get more information about Edwards’ syndrome, Patau’s syndrome and living with people with these conditions from SOFT UK at SOFT UK - Support Organisation for Trisomy 13 and Trisomy 18.

What will the screening test result tell me?

The screening test can tell you what chance you have of your baby having one of the conditions. The tests will not be able to tell you how affected your baby might be.

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

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

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:

  • no further testing, or
  • 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 an invasive test called 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 screening test or not. Some women want to find out if their baby has these conditions, 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. Your decision will be respected and health-care professionals will support you whatever you decide. 

The scans you have in pregnancy can occasionally see things that may identify that your baby could have one of these syndromes and you may be offered an invasive test at this stage.

What screening test will I be offered?

Combined screening

You will be offered an ultrasound scan (if possible, they will measure the small space nuchal translucence at the back of your 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 the chance of your baby having 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 be offered this test.

Sometimes it is difficult to measure the space at the back of your 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 your 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.

Where can I have the test done?

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

Results

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’.

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.

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 4% of women (that is, between two and four out of 100) who have the combined or quadruple screening tests 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 your 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 this test it takes usually about two weeks to get the result.  In about 2% (2 out of 100 pregnancies) of cases the NIPT test will not be able to give a result and you will be offered an invasive test or you may decide to have no further tests.

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

Below is some basic information about the invasive procedures you could be offered if you have the screening tests and receive a higher chance result. More information is available from your midwife or your hospital doctor (your obstetrician) or from Antenatal Screening Wales/ Sgrinio Cyn Geni Cymru | Antenatal Screening Tests.

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 after you are 11 weeks and before 14 weeks pregnant. Having a CVS carries a risk of 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 your 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.

Having an amniocentesis carries a risk of miscarriage in around 1% of pregnancies (1 out of every 100 pregnancies).  If you are having twins the risk of miscarriage will be around 2% (2 out of every 100 pregnancies).

What would an invasive test result tell me?

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

More information

You can get information about Down’s syndrome, Edwards’ syndrome and Patau’s syndrome screening from your midwife or your hospital doctor (your obstetrician) or from support organisations.

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)

  • Email: enquiries@soft.org.uk
  • Website: www.soft.org.uk

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 or 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 a 1 to 2% risk of miscarriage to find this out?

  • Would I continue with the pregnancy if my baby has 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 first test, would I want to have a NIPT blood test knowing that it could come back high chance?
  • Would I be happy to take the NIPT test in the hope it would come back low chance?
  • How important would finding out sooner be (using the invasive test that risks a miscarriage) rather than delaying the result for a NIPT test that may rule out the condition?

 

 


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