Screening for Downs, Edwards and Pataus Syndrome
Choosing whether to have screening for Downs, Edwards or Pataus Syndrome is an important decision, for you and for your baby.
Your midwife will talk to you about the tests available to you 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 for Downs, Edwards or Pataus Syndrome to help you decide whether to be screened.
There is some really useful information on NHS Choices about Down’s, Edward and Patau’s which we suggest you read.
In Downs syndrome there is an extra chromosome 21 in each cell.
A baby born with Down’s syndrome will have a learning disability. This means they will find it harder than most people to understand and to learn new things. They may have communication problems and difficulty managing some everyday tasks. It is impossible th know what level of learning disability a baby with Down’s syndrome will have.
In Edwards’ syndrome there is an extra copy of chromosome 18 in each cell.
A baby affected with Edwards’ syndrome will usually die before they are born, be stillborn or die shortly after birth, rarely some may survive to adulthood. They can have heart problems, unusual head and facial features, growth problems and be unable to stand or walk.
In Patau’s syndrome there is an extra copy of chromosome 13 in each cell.
A baby affected with Patau’s syndrome will usually die before they are born, be stillborn or die shortly after birth, rarely some may survive to adulthood. They can have heart problems, a cleft lip and palate, growth problems, poorly formed eyes and ears, problems with their kidneys and be unable to stand or walk.
Testing for Down’s, Edwards’ or Patau’s Syndrome
Screening for these syndrome’s is offered to pregnant women of all ages. The tests can provide information about the chance of a baby having these syndrome’s. These tests use blood samples taken from the mother and measurements taken from ultrasound scans. The tests you will be offered depend on how many weeks pregnant you are.
Screening in early pregnancy
The combined test uses the results of a blood test and an ultrasound scan to calculate the risk (chance) of your unborn baby having Down’s, Edwards or Patau’s Syndrome. An ultrasound scan is carried out at 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 risk (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 between 14 weeks and 2 days to 20 weeks of pregnancy. This test looks at different substances to those measured in early pregnancy. This test is known as the quad (or quadruple) test. However this test is only for Down’s Screening.
It is important to remember that if you would like a screening test for Edwards or Pataus this can only be done up to 14+1 weeks of pregnancy. Down Syndrome only can 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 Syndrome screening.
A letter will be sent to you with your risk (chance) result - for example 1:250 (1 in 250). This result would be classed as a "low risk" screening result as all results below 1:150 are classed as "low risk". It is important to remember with any screening test that "low risk" does not mean "no risk" but the chances of having an affected baby are very small.
High risk results
If you get a higher risk (increased risk) result from a screening test it means that we will offer you more tests. It does not mean that your baby definitely has Down’s Edwards’ or Patau’s Syndrome.
You will be contacted by an antenatal midwife, usually by telephone and invited into the hospital to discuss your result and what options there are for further tests. You will be offered a diagnostic test which can tell you definitely whether your baby is affected.