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Edwards’ syndrome is a genetic disorder caused by the presence of an extra chromosome 18. This is why it also goes by the name trisomy 18. This condition is rare and it occurs in around 1 in 5,000 live births.
According to the Office for National Statistics (ONS), there were 95 live births with Edwards’ syndrome in England and Wales in 2019. Sadly, ONS data also shows that the mortality rate for babies with Edwards’ syndrome in England and Wales was 98.1% for the same year. In this article, we’ll tell you everything you need to know about Edwards’ syndrome.
What is Edwards’ syndrome?
Edwards’ syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 18 in some or all of the body’s cells. Normally, humans have two copies of each chromosome (one from each parent) and have 46 in total. However, with Edwards’ syndrome, there are three copies of chromosome 18, which means 47 chromosomes in total.
Since there is extra genetic material, there is a range of associated abnormalities. This presents itself both physically and developmentally and is, in most cases, fatal. The condition affects multiple systems in the human body and those with the condition have a variety of medical problems. This includes feeding difficulties, heart defects, breathing problems, skeletal abnormalities, and kidney abnormalities. They can also have developmental delays and intellectual disabilities.
What causes Edwards’ syndrome?
In Edwards’ syndrome, there is an error in cell division during the development of the egg or sperm, or early in embryonic development. This results in the foetus having an extra copy of chromosome 18.
There are different ways that this happens:
1. Non-disjunction: around 95% of cases of Edwards’ syndrome are down to non-disjunction. This means that the chromosomes don’t separate properly during the cell division process. As a result, the sperm or egg cell has an extra copy of chromosome 18.
2. Mosaicism: for some cases of Edwards’ syndrome, the extra chromosome 18 isn’t found in all of the cells in the body. This is called mosaicism and happens when there’s an error in cell division occurring during the early stages of embryonic development after fertilisation.
3. Translocation: a few cases of Edwards’ syndrome are the result of a piece of the 18th chromosome breaking off and attaching to another chromosome. This results in the person having an extra copy of some of the genetic material from the 18th chromosome.
The risks of having a child with Edwards’ syndrome increase with maternal age. However, this is not the only factor involved.
Other risk factors are:
- Having a previous pregnancy with a child with Edwards’ syndrome. Women who have had a pregnancy or child with Edwards’ syndrome have an increased risk of the condition being present in a subsequent child.
- Family history of chromosome abnormalities. In rare cases, Edwards’ syndrome is caused by a genetic translocation. If a parent carries this translocation, they could pass it on to their children.
- Maternal radiation exposure. There is evidence to suggest that being exposed to a high level of radiation can increase the risk of chromosome abnormalities, like Edwards’ syndrome.
- Medication use. Certain medicines, including some anti-seizure medicines, have been associated with an increased risk of chromosome abnormalities like Edwards’ syndrome.
It is important, however, to note that the vast majority of cases of Edwards’ syndrome occur spontaneously and are not down to behaviours or risk factors.
Types of Edwards’ syndrome
Since there are three main causes of Edwards’ syndrome, there are also three types of the condition. The severity of the syndrome can vary widely. This depends on the specific genetic abnormality and how much extra genetic material there is.
All types of Edwards’ syndrome can cause significant problems and developmental delays.
Here are the different types:
Full trisomy 18
95% of cases of Edwards’ syndrome are full trisomy 18 whereby a person has three copies of chromosome 18 in every cell. This extra genetic material causes life-threatening abnormalities.
Mosaic Edwards syndrome
This is the type of Edwards’ syndrome described when the cell division error happens after fertilisation. The egg and the sperm were, themselves, normal but something went wrong after they fertilised.
Partial Edwards’ syndrome
This is translocation trisomy 18 when parts of the 18th chromosome have broken off and attached to another chromosome. Sometimes, this results in the person having some extra copies of genetic material from the chromosome but not a full extra copy of it.
How is Edwards’ syndrome diagnosed?
There is a range of methods used to diagnose Edwards’ syndrome.
1. Prenatal testing: this can be used to detect Edwards’ syndrome in a developing foetus. There are two types of testing that can be done when the baby is in the womb.
Non-invasive prenatal testing (NIPT)
This is a blood test capable of analysing the foetus’s DNA. This DNA is present in the mother’s blood and it’s called cell-free DNA or cfDNA. The test looks for abnormalities in the number of chromosomes. This is a test that is offered to women who are at an increased risk of having a baby with a chromosome abnormality and it can be done after the 10th week of pregnancy.
The NIPT has an accuracy rate of more than 99%. It’s important to note that the NIPT is a screening test rather than a diagnostic test. A positive NIPT result needs to be confirmed with a diagnostic test like amniocentesis or chorionic villus sampling (CVS).
If a woman doesn’t qualify for NIPT on the NHS but still wants this testing done, it is possible to go private through a company called Harmony. Besides checking for Edwards’, this test can look for all chromosomal abnormalities and can even confirm the sex of the baby from as early as 10 weeks.
Invasive prenatal testing
This involves taking a sample of cells directly from the foetus growing in the womb. This is either through chorionic villus sampling (CVS) or amniocentesis. This type of test is more invasive than the NIPT test and it does carry a risk of miscarriage, though this is small. It is, however, more accurate in diagnosing the condition.
Chorionic Villus Sampling (CVS)
This prenatal test involves taking a sample of tissue from the placenta as this organ contains foetal genetic material. CVS is usually carried out between week 10 and week 13 of pregnancy and it involves inserting a needle into the uterus to collect the same. This is done either transabdominally (through the skin on the abdomen) or transcervially (through the cervix).
This is a definitive diagnostic test and can show with 100% accuracy whether a foetus has Edwards’ syndrome (or another abnormality).
CVS does come with risks. There is a very small risk (less than 1%) of miscarriage or infection.
If a baby is presenting with signs and symptoms of Edwards’ syndrome, they will have a diagnostic test like a chromosome analysis to confirm the diagnosis.
In some cases, Edwards’ syndrome might be suspected based on physical characteristics and developmental delays. A healthcare provider might order extra tests like a chest X-ray or echocardiogram to look for heart abnormalities that are common with Edwards’ syndrome.
How common is Edwards’ syndrome?
This chromosomal abnormality is relatively rare and only occurs in around 1 in 5,000 live births. Slightly more girls are affected than boys.
There is some evidence to suggest that this syndrome is more common in certain ethnic groups. For example, a study in the journal Prenatal Diagnosis found that the incidence of Edwards’ syndrome was higher among babies born to black and South Asian mothers in the United Kingdom compared to babies born to white mothers. The reasons for this aren’t quite clear and more research is needed.
It is important to note, however, that the incidence of the syndrome is relatively consistent across different countries, although there is likely to be some variation depending on factors such as maternal age and the availability of prenatal screening and diagnostic testing.
What are the effects of Edwards’ syndrome?
Edwards’ syndrome can cause a range of physical and developmental abnormalities, which can vary in severity and impact on a child’s health and development.
Some of the effects on the child may include:
- Developmental delays: Babies with Edwards’ syndrome may experience delays in reaching developmental milestones like sitting, crawling and walking.
- Feeding difficulties: Babies with Edwards’ syndrome might find feeding difficult. This can lead to poor growth and malnutrition.
- Heart defects: Edwards’ syndrome is associated with heart abnormalities, and these can range from mild to severe.
- Breathing problems: Some babies with Edwards’ syndrome might have weak respiratory muscles. This can make it difficult for them to breathe.
- Intellectual disability: The majority of babies with Edwards’ syndrome have an intellectual disability. This means they might have difficulty with learning and understanding.
- Physical abnormalities: There is a range of physical abnormalities associated with Edwards’ syndrome. This includes a small head, low-set ears, a cleft palate or lip and abnormal fingers and toes.
- Shortened lifespan: Most babies born with Edwards’ syndrome do not survive beyond their first birthday.
It’s important to note that the severity of the effects of Edwards’ syndrome will be varied and not all babies will have the same problems.
Effects on the pregnancy
As well as having effects on the baby, Edwards’ syndrome can have an effect on the pregnancy too.
- An increased risk of miscarriage: Many pregnancies affected by Edwards’ syndrome will end in miscarriage. This is often in the first trimester.
- If a baby does survive the pregnancy, there is an increased risk of stillbirth.
- There is often an association of Edwards’ syndrome with polyhydramnios. This is an excess of amniotic fluid in the uterus. This happens because the baby has problems with its swallowing reflex.
- Reduced foetal movements can occur and this often indicates the baby is in distress.
- There might be noted abnormal ultrasound findings. This might be a small head circumference, or abnormalities with the heart, brain, kidneys or other organs.
Physical presentation of Edwards’ syndrome
We know that the symptoms of this condition can differ from one person to another but there are some common physical signs.
- Undescended testicles.
- Underdeveloped fingernails.
- Unusual chest shape.
- Feet that are rounded underneath.
- Clenched hands.
- Low birth weight.
- Missing or underdeveloped thumbs.
- Crossed legs.
- Toe webbing (second and third).
- Upturned nose.
- Small, widely spaced eyes and narrow folds on the eyelids.
- Heavy/drooping eyelids.
- Low-set ears.
- Small jaw.
- Small head.
- Iris clefts.
- Umbilical hernia.
- Diastasis recti.
Living with Edwards’ syndrome
A diagnosis of Edwards’ syndrome is typically given when the baby is still in utero through prenatal screening. The diagnosis has a huge impact on the baby as well as their wider family.
For the baby, there are often significant problems with development and abnormalities, which mean that most babies do not live past their first birthday. There are, however, cases where people do live with the condition. Though it is difficult to know how many people are living with the condition, with it occurring in one in every 5,000 births, there are likely several thousands of people living with it. If a child does survive, they will typically require ongoing medical care and support throughout their lives.
It is reported that the average lifespan is between 5 to 15 days, with 8% of infants being able to live over one year. Around 1% live up to ten years old. Very few will survive to adolescence.
An Edwards’ syndrome diagnosis can have a significant impact on the parents and the wider family. Since survival rates are generally low, the psychological and emotional impact of this diagnosis can be profound. Parents may experience a wide range of emotions, including shock, anger, grief, guilt and anxiety.
When faced with this diagnosis, parents often need to make a decision about the pregnancy, including whether to terminate or continue. They also need to be prepared for the possibility of having to care for a child with significant developmental and health needs. This might involve accessing medical care, support services and charities associated with the condition.
All families have a unique experience when they’re faced with an Edwards’ syndrome diagnosis. The impact this has will depend on a range of factors, including how severe the diagnosis is, the family’s values and beliefs and the availability of resources and support.
Treatment for Edwards’ syndrome
Currently, there is no cure for Edwards’ syndrome. Treatments are focused on managing the symptoms and any associated health problems. The specific interventions and treatments will depend on the severity of the condition and the individual’s needs.
Sometimes surgery may be required to correct structural abnormalities like gastrointestinal problems and heart defects. Difficulties with breathing and feeding might also need specialist input like tube feeding or respiratory support.
It’s possible to target developmental delays and intellectual disabilities with interventions like speech therapy, occupational therapy and physiotherapy. There are also interventions for behaviour and education too.
Managing Edwards’ syndrome is complex and it can require a large team of different healthcare professionals like doctors, nurses and therapists.
In the United Kingdom, there are a number of support services and organisations available for families facing a diagnosis of Edwards’ syndrome. These organisations can provide emotional support, practical assistance and information for families.
One well-known organisation is SOFT UK (Support Organisation for Trisomy 13/18 and Related Disorders). This charity offers information, support and advocacy for those affected by Edwards’ syndrome as well as other conditions like Down syndrome.