Screening for Down, Edwards and Patau syndromes during pregnancy

What syndromes do we screen for in pregnancy?

Inside the cells of our bodies are 46 chromosomes; these contain all our genes and are arranged in 23 pairs. An egg and a sperm usually carry one of each chromosome which then pair up again when the egg is fertilised. Occasionally, as the egg or sperm are developing, something doesn’t go to plan and they end up with an extra part of, or a whole chromosome. This means that when the egg is fertilised there is too much of a particular chromosome, so too many genes. This can have impact on how the baby develops. Nothing the parent does or does not do can affect the dividing of the chromosomes.

The most common chromosome that this happens with is number 21 – the baby inherits 3 sets of number 21 chromosome. This is called Down syndrome or Trisomy 21. The next most common are with numbers 18 and 13, these are called Edwards syndrome (Trisomy 18) and Patau syndrome (Trisomy 13). Although we know that the chances of having a baby with one of these “Trisomies” increase with age, younger Mum’s can have babies with them too.

People with Down syndrome, like everyone, vary a great deal in appearance, personality and ability. There will always be a certain degree of learning difficulties but these can vary with each individual and cannot be predicted at birth. There are a number of health problems associated with Down syndrome but these too will vary from person to person. Edwards and Patau syndromes are rarer than Down syndrome but much more serious. Many babies with Edwards and Patau syndromes are often miscarried or still born and sadly, if these babies are born alive, most will not survive the first few months of life. They will often have problems with a number of their organs and will need a lot of supportive care. More information can be found in your “Screening tests for you and your baby” booklet.

For further information about Down, Edwards and Patau syndromes contact

 

Screening for Down, Edwards and Patau syndromes at Norfolk & Norwich University Hospital.

Screening for these syndromes is optional but all pregnant women are offered the screening tests and can opt to be screened for: –

  • all 3 syndromes
  • Down syndrome only
  • Edwards and Patau syndromes only.

This page has information about the tests available at the Norfolk and Norwich University Hospital. Your community midwife will explain all these tests but if you have any further questions you can contact the Antenatal Screening Coordinator, Alison Evans on 01603 286802.

Screening can be performed either between 11+2 – 14+1 weeks by combining information from a scan and a blood test (Combined Test) or from 14+2 – 20+0 weeks of pregnancy by a blood test alone (Quadruple Test). The information sheet Screening for Down, Edwards and Patau syndromes in Pregnancy has more detailed information about each test. The type of test you are offered will depend on certain criteria. Unfortunately there is no screening test available if you are found to be over 20 weeks pregnant, but if any problems are seen on your 20 week or fetal anomaly scan that could be associated with any of these syndromes, the sonographer will discuss this with you and you will be referred to a specialist to discuss them further.

If your screening result shows an increased or higher risk of any of the syndromes you will be contacted directly to discuss the result and be offered a diagnostic test, either CVS or amniocentesis. A diagnostic test is sampling the pregnancy to look at cells, either from the placenta or the baby, so will be able to tell whether a baby has one of these syndromes or not. Unfortunately these tests do have a small chance of miscarriage so they too are optional. You will get the opportunity to discuss this fully if you are at increased risk. Please click on the links below for information about the diagnostic tests.

Chorionic Villus Sample (CVS)

Amniocentesis

 

Do the screening tests identify anything else?

One of the hormones measured in the Combined test is called Pregnancy Associated Plasma Protein-A (PAPP-A). Occasionally the blood test will show a low level of PAPP-A. This by itself does not put the baby at risk of having one of these syndromes, but we know that sometimes the baby can grow more slowly in later pregnancy. If this is the case you will be contacted directly and further appointments will be arranged later in pregnancy to check how your baby is growing.

One of the hormones measured in the Quadruple test is called Alpha-fetoprotein (AFP). AFP can be raised when there is a problem such as Spina bifida. If your level is higher, you will be contacted directly and offered an appointment for an ultrasound scan. An ultrasound scan allows us to check the baby in great detail and will usually identify the problem if there is Spina bifida. Most women with an increased hormone level will go on to have a baby without Spina bifida.

 

Useful Links

The tests we offer at the Norfolk & Norwich University Hospital are those recommended by the UK National Screening Committee UKNSC. The following websites contain more information about screening in general as well as offer help to women deciding whether to opt for screening or not. ARC also offers support to women and their families when they are given a higher risk result.

       ARC (Antenatal Results and Choices)

o   0207 631 0285

o   www.arc-uk.org

 

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