What is Edward’s syndrome?

Here, we look at Edwards’ syndrome, what causes it, characteristics, and how you can screen for Edwards’ syndrome during pregnancy.

The AlphaBiolabs NIPT is a screening test, used to find out if a pregnant woman is carrying a foetus with an increased chance of being affected by a chromosomal condition, known as an aneuploidy. An aneuploidy is a condition caused by having an incorrect number of chromosomes i.e. an extra or a missing copy of a chromosome.

This test is a simple blood test with no risk to the mother or the baby, and can be carried out from as early as 10 weeks.

The three most common chromosomal conditions covered by the Standard AlphaBiolabs test are:

1. Down’s syndrome (Trisomy 21)
2. Edwards’ syndrome (Trisomy 18)
3. Patau’s syndrome (Trisomy 13)

Down’s syndrome is by far the most common chromosomal aneuploidy included in this screening test. As well as Down’s syndrome, the Standard AlphaBiolabs NIPT test also screens for Edwards’ syndrome, and Patau’s syndrome, which are much more serious than Down’s syndrome – babies born with these conditions rarely survive past infancy.

Additionally, the Advanced AlphaBiolabs NIPT test can also detect all other aneuploidies, including Autosomal Aneuploidies (AAs) and Sex Chromosome Aneuploidies (SCAs) such as Turner’s syndrome, Klinefelter’s syndrome, Jacob’s syndrome and Trisomy X.

In this article, we focus on Trisomy 18, also known as Edwards’ syndrome.

What is Edwards’ syndrome?

Edwards’ syndrome is a very rare but serious chromosomal condition. It is caused by having a full or partial extra copy of chromosome 18 and is sometimes referred to as Trisomy 18.

Sadly, around 70% of Trisomy 18 pregnancies end in miscarriage or stillbirth, and very few babies (13 in 100) survive past their first birthday.

Having a baby with Edwards’ syndrome (an extra copy of chromosome 18) occurs as a result of a change in the egg or sperm, usually before the baby is conceived. This is a random chance event, and even though the risk of having a baby with Edwards’ syndrome increases with age, anyone can have an affected pregnancy.

How common is Edwards’ syndrome?

Edwards’ syndrome is a very serious and rare condition. Around 1 in 400 pregnancies are diagnosed with Edwards’ syndrome. However, the number of live births of babies with Edwards’ syndrome ranges from 1 in 3,600 to 1 in 10,000 and is dependent on the country and its termination policies. Therefore, very few pregnancies affected by Edwards’ syndrome result in live birth. This is because around 70% of affected pregnancies end in miscarriage or stillbirth, and very few live births (13%) survive past one year.

What causes Edwards’ syndrome?

Edwards’ syndrome is caused by having an extra critical portion of chromosome 18. This imbalance of chromosomes can be present in all or some cells that make up the body. Passing on an extra copy of chromosome 18 occurs by random chance, and even though we know that the likelihood of having a baby with Edwards’ syndrome increases with age, anyone can have an affected pregnancy. In most cases, Edwards’ syndrome is not hereditary and does not run in families.

Can HIV cause Edwards’ syndrome?

HIV does not affect the risk of having a pregnancy affected by Edwards’ syndrome. Edwards’ syndrome is most often caused by a chance event that occurs in the egg or sperm before fertilisation. Even though the risk increases with age, it is not caused by anything that either parent did before or during pregnancy.

What are the different types of Edwards’ syndrome?

If a baby has Edwards’ syndrome, they inherited a full or partial extra copy of chromosome 18, which can be present in all or some of their cells. More than 90% of Edwards’ syndrome instances are caused by Trisomy 18 (having an extra full copy of chromosome 18 in all cells). The remaining 10% of cases are caused by one of two rare genetic occurrences.

Full form

The full form (trisomy 18) is the most common and most severe type of Edwards’ syndrome and occurs when a person has a full, separate, extra copy of chromosome 18. It accounts for over 90% of all Edwards’ syndrome cases.

Mosaic form

Around 5% of babies born with Edwards’ syndrome will have a less severe form, known as mosaic Edwards’ syndrome. These individuals will have an extra copy of chromosome 18 in some, but not all of the cells in their body.

Partial form

The remaining cases of Edwards’ syndrome are caused by having an extra portion of chromosome 18, rather than an entire extra chromosome. This is an incredibly rare form of Edwards’ syndrome.

Is Edwards’ syndrome hereditary?

Edwards’ syndrome does not usually run in families and is therefore not hereditary. However, in very rare instances, Edwards’ syndrome has a hereditary component, meaning that it has been passed on from a parent to a child through genes.

What can impact the probability of having a child with Edwards’ syndrome?

The risk of having a pregnancy affected by Edwards’ syndrome increases with maternal age. This means that older women have an increased chance of having a baby with Edwards’ syndrome.

However, the majority of cases of Edwards’ syndrome are caused by a random event that occurs within the egg or sperm prior to conception. This means that anyone can have a baby with Edwards’ syndrome.

In very rare cases, healthy individuals who carry a balanced chromosomal translocation can be at an increased risk of having a pregnancy affected by Edwards’ syndrome.

What are the characteristics/features/symptoms of Edwards’ syndrome?

Edwards’ syndrome is a very serious condition. Over 70% of Edwards’ syndrome pregnancies result in miscarriage or stillbirth and only 13% of babies that are born survive past their first birthday.

All babies born with Edwards’ syndrome will have a level of learning disability, which is often very severe, and many health challenges.

Usually, babies with Edwards’ syndrome will have a low birthweight and problems with feeding and breathing. Health complications include respiratory, heart, kidney, and digestive problems.

Even though survival is rare, babies born with full Edwards’ syndrome can slowly make progress in their development. Babies born with partial or mosaic Edwards’ syndromes often have a better prognosis and can have an increased life expectancy, despite their complex physical and mental needs.

What is the treatment for Edwards’ syndrome?

There is no cure for Edwards’ syndrome. Babies born with Edwards’ syndrome have a poor prognosis and survival past one year is rare. Treatments are based on each individual’s medical, developmental and intellectual needs. Babies born with Edwards’ syndrome often have difficulty feeding, and may be fed through a feeding tube.

How can I get Edwards’ syndrome screening during pregnancy?

A traditional screening test for Edwards’ syndrome, Down’s syndrome, and Patau’s syndrome is available at 11-13 weeks of pregnancy. Known as a ‘combined’ test, it comprises a blood test and an ultrasound scan.

The blood test looks at markers found in the blood that can indicate an increased chance of carrying a baby with a chromosomal disorder, while the ultrasound scan is used to determine something known as the ‘nuchal translucency’.

The results of both these tests, along with the age of the pregnant woman, determine the risk of carrying a foetus with Edwards’, Down’s, or Patau’s syndrome.

In the case of a high-risk result, the pregnant woman will be offered the chance to receive non-invasive prenatal genetic testing (NIPT), another screening test, or diagnostic testing.

Diagnostic testing typically involves amniocentesis or chorionic villus sampling (CVS). For amniocentesis, a long, thin needle is inserted into the abdomen to obtain a sample of amniotic fluid for testing. For CVS, a needle is inserted into the womb to obtain a sample of cells from the placenta.

These tests will provide a definite answer as to whether or not the baby has Edwards’, Down’s, or Patau’s syndrome. However, both tests are invasive and carry a small risk of miscarriage.

For this reason, many pregnant women are choosing private NIPT screening, as it is non-invasive, and available to all expectant mothers irrespective of whether they were classified as high risk by the combined test.

For an AlphaBiolabs NIPT, all that’s required is a blood sample, which is collected from the mother’s arm. This makes the test 100% safe for mum and baby, with no risk of miscarriage.

The test uses next-generation sequencing to analyse cell-free foetal DNA (cffDNA) – fragments of the baby’s DNA that naturally circulate in mum’s bloodstream during pregnancy – and detect chromosomal abnormalities, including Edwards’ syndrome.

How AlphaBiolabs NIPT compares to traditional screening tests:

	Traditional screening tests	AlphaBiolabs NIPT
Number of tests	Multiple procedures over the course of the first and/or second trimester	One blood test that can be taken from as early as 10 weeks gestation
What does it screen for?	Combined screening identifies around 85% of babies with Down’s syndrome and 80% of babies with Edwards’ or Patau’s syndrome	Over 99.99% accurate for detecting chromosomal abnormalities
Screening in twin pregnancies	Reduced performance of screening in twin pregnancies	Equivalent performance of screening in both twin and singleton pregnancies
Speed of results	Results are provided following several tests, which can take some time	Results provided within 6 business days
Sample collection	Can involve invasive methods, carrying an increased chance of miscarriage	Blood sample taken from mother’s arm – non-invasive and 100% safe for mum and baby
Can you find out the baby’s sex?	No early gender identification	Optional foetal sex determination, at no extra cost