About Down's Syndrome : Pre-natal FAQs

The Down’s Syndrome Association is a source of balanced, accurate information and advice.

Here you will find answers to questions that we are often asked. Our Information Officers are happy to answer any questions you have and provide you with further information – we talk to parents at any stage of pregnancy. You can download this information here or call for a hard copy of this document.

You can call us on 0333 1212 300 or email info@downs-syndrome.org.uk

Please click on a FAQ below to expand.

Screening Tests

What screening tests will I be offered by the NHS?

Screening for Down’s syndrome is offered to pregnant women of all ages. The tests can provide information about the chance of a baby having Down’s syndrome. 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. A screening test can only provide you with information about the likelihood of having a baby with Down’s syndrome.

Do I have to take the tests?

No, it is your choice whether or not to take the tests. If you decide to take the tests, think about why you are taking the test, what the test can tell you and what choices you may have to make as a result of taking the test. You need to make informed choices that are right for you. Health professionals are there to help, so feel free to ask them any questions you have about screening before you decide whether to go ahead with or decline the tests.

The combined test offered in early pregnancy

The combined test uses the results of a blood test and an ultrasound scan to calculate the chance of the unborn baby having Down’s syndrome.

A blood sample taken from the mother between 10 weeks to 14 weeks + 1 day of pregnancy is used to measure the amount of some substances that are found naturally in the mother’s blood. These substances are passed to the mother from the baby.

An ultrasound scan is carried out between 11 weeks + 2 days and 14 weeks + 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 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 to work out this 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 + 2 days to 20 weeks of pregnancy. This test looks at different substances to those measured in early pregnancy. Like the combined test, a computer program uses the results and the mother’s details to work out a chance figure. These tests are known as the quad (or quadruple) test.

What is considered to be a higher chance of having a baby with Down’s syndrome?

If the screening test shows that the chance of the baby having Down’s syndrome is between 1 in 2 and 1 in 150 this is called a higher chance result.

If the screening test shows that the chance of having a baby with Down’s syndrome is lower than 1 in 150, this is a lower chance result. A lower chance result does not mean there is no chance at all of the baby having Down’s syndrome.

If I have a higher chance figure does that mean that my baby has Down’s syndrome?

No, only a diagnostic test can tell you for sure if your baby has Down’s syndrome.

Do screening tests that are currently available from the NHS identify all babies with Down’s syndrome?

No, although some of the 750 babies with Down’s syndrome born each year in the UK will have been diagnosed pre-natally.

Non invasive pre-natal testing (NIPT)

Non invasive pre-natal testing (NIPT) for Down’s syndrome involves a blood sample being taken from the mother. The sample is sent to a laboratory, this may be in the UK or overseas. The sample will be tested for the amount of cell-free fetal DNA (cffDNA) present, particularly chromosome 21. The presence of an extra copy of chromosome 21 in the body’s cells is what causes Down’s syndrome. Cell-free fetal DNA originates in the placenta. Each chromosome has strings of DNA that are specific to that particular chromosome. So by analyzing the DNA strings that link to each chromosome, the amount of chromosome 21 in the blood sample can be compared to the amount of the other chromosomes. The total amount of chromosome 21 in the blood sample is then used to calculate the likelihood of the baby having Down’s syndrome.

The test can also be used to look for Edwards’ syndrome and Patau’s syndrome.

NIPT is an enhanced screening test, not a diagnostic test. NIPT can be carried out from 10 weeks of pregnancy. It is usually combined with an ultrasound scan.

Although NIPT is thought to be very accurate, it is possible for the results to be incorrect – to indicate a higher chance for Down’s syndrome when the baby does not have Down’s syndrome, or fail to indicate a higher chance when the baby does have Down’s syndrome. For the time being an invasive diagnostic test (amniocentesis or CVS) is still required to confirm a definitive diagnosis of Down’s syndrome.

My father had a relative with Down’s syndrome; does this mean that I have a higher chance of having a baby with Down’s syndrome?

For around 99% of people, Down’s syndrome occurs as a result of a chance happening at around the time of conception. There are three types of Down’s syndrome: trisomy 21 (nondisjunction), translocation and mosaicism. 1% of people with Down’s syndrome have a very rare form which can be inherited. This only occurs in some cases of Down’s syndrome resulting from translocation. Relatives of a person who has this rare type of translocation have an increased chance of being translocation carriers.

What happens next if I have a higher chance of having a child with Down’s syndrome?

Your midwife or doctor will discuss the screening test results with you and answer any questions that you have. You will be offered a diagnostic test which can tell you whether your baby has Down’s syndrome or not.

Diagnostic Tests

What types of diagnostic test are available?

There are two diagnostic tests available – chorionic villus sampling (CVS) and amniocentesis. CVS can be performed from weeks 10 to 22 of pregnancy although it is usually performed between weeks 11 and 13. Amniocentesis is usually carried out from week 15 of pregnancy.

Are the diagnostic tests safe?

These procedures are not completely safe because they are invasive. The overall chance of having a miscarriage after CVS is about 1 to 2%. In other words, about one or two in every 100 women who have CVS will miscarry. For amniocentesis, the rate is about one in 100. These figures vary slightly from hospital to hospital. If you would like to know the miscarriage rates after CVS or amniocentesis in your hospital, please ask your doctor or midwife.

Do I have to take the diagnostic test? Should I take the diagnostic test?

If you do get a higher chance result from a screening test, your midwife or doctor should give information and support. You will need time to make up your mind about what to do next. It is your choice whether or not to take a diagnostic test.

If you are in this position it is important to understand that you have a difficult decision to make. You have two options. You may feel that you don’t want to know so you decide not to have a diagnostic test.

The other option is to have the diagnostic test, knowing that this will slightly increase the chance of miscarriage. Before you take the diagnostic test, you need to think about the choices that you will have to make if you are given a positive diagnosis.

Sometimes it helps if you think about your chance of having a baby with Down’s syndrome alongside the chance of having a miscarriage if you take a diagnostic test.

If you have a positive diagnosis the knowledge your baby has Down’s syndrome may inform the management of your pregnancy and your birth plan in a helpful way.

Aren’t most babies born with Down’s syndrome born to older mothers?

Although the chance of having a baby with Down’s syndrome increases with the mother’s age, babies with the syndrome are born to mothers of all ages. Over half of children with Down syndrome are born to mothers under the age of 35 years.

How many children with Down’s syndrome are born each year in UK?

One in every 1000 babies born in the UK is born with Down’s syndrome. Approximately 750 babies with Down’s syndrome are born in the UK each year.

Why do I have a higher chance/positive diagnosis?

Down’s syndrome occurs in people of all races, religions and economic backgrounds and in all countries around the world.

As yet, no one knows what causes the presence of the extra copy of chromosome 21. There is no way of predicting whether a person is more or less likely to make an egg or sperm with an extra chromosome. As far as we know, nothing done before or during pregnancy causes the condition.

I have heard that people with Down’s syndrome have a learning disability; can the tests tell me the level of my unborn baby’s learning disability?

It is true that everyone with Down’s syndrome will have a level of learning disability. However, Down’s syndrome affects each individual child in different waysso it is not possible to know how the condition will affect the child’s learning potential before birth.It is not possible to predict how the child will develop or what the person might achieve either before or after birth.Our helpline staff will be pleased tosend youinformation about thelives of people with Down’s syndrome and guide you to information on our website.

I have had a pre-natal diagnosis or I already have a child with Down’s syndrome, what is the chance of having another baby with the condition?

Parents with one baby with Down’s syndrome are usually told that the chance of having another baby with Down’s syndrome is 1 in 100. Very few families are known who have more than one child with Down’s syndrome. There are differences of opinion as to how the quoted figure of 1 in 100 should be interpreted for older mothers who already have one child with Down’s syndrome.

If you are considering becoming pregnant again, you can ask your GP for a referral to your local genetic counseling service. You can discuss the likelihood of having another baby with Down’s syndrome with a genetic counsellor.

Resources


DSA

You will find lots of information and resources about people with Down’s syndrome on the DSA’s website www.downs-syndrome.org.uk including the following publications

Looking Forward to Your Baby

Celebrating our Lives – Adults with Down’s syndrome

People with Down’s syndrome – Your Questions Answered

You can download these from DSA’s website or call us (Tel: 0333 1212 300) for hard copies.

ARC (Antenatal Results and Choices)

Website http://www.arc-uk.org/

Helpline: 0845 077 2290 (Mon to Fri 10.00 am to 5.30pm) or 0207 713 7486 via mobile.

NHS – Screening for Down’s syndrome

http://www.nhs.uk/conditions/pregnancy-and-baby/pages/screening-amniocentesis-downs-syndrome.aspx

Did you know…?


  • Around one in every 1000 babies born in the UK will have Down’s syndrome.
  • There are approximately 40,000 people in the UK with the condition.
  • Although the chance of a baby having Down’s syndrome is higher for older mothers, more babies with Down’s syndrome are born to younger women.
  • Down’s syndrome is caused by the presence of an extra chromosome in a baby’s cells. In the majority of cases, Down’s syndrome is not an inherited condition. Down’s syndrome usually occurs because of a chance happening at the time of conception.
  • Down’s syndrome is not a disease. People with Down’s syndrome are not ill and do not “suffer” from the condition.
  • People with the syndrome will have a learning disability. The learning disability affects a person’s ability to learn, it does not mean they cannot learn.
  • Today the average life expectancy for a person with Down’s syndrome is between 50 and 60 with a small number of people living into their seventies.

About the Down’s Syndrome Association


  • Last year we responded to over 8,500 telephone enquiries on our switchboard from members, professionals and the general public, and over 3,800 calls on our helpline.
  • Our website was visited by over 466,034 people from over 150 countries worldwide.
photograph: Eleonora_os/Shutterstock.com

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