Edwards' syndrome (trisomy 18)

Edwards' syndrome, also known as trisomy 18, is a rare but serious genetic condition that causes a wide range of severe medical problems.

Sadly, most babies with Edwards' syndrome will die before or shortly after being born.

Some babies with less severe types of Edwards' syndrome, such as mosaic or partial trisomy 18, do survive beyond a year and, very rarely, into early adulthood. But they are likely to have severe physical and mental disabilities.

Cause of Edwards' syndrome

Each cell in your body normally contains 23 pairs of chromosomes, which carry the genes you inherit from your parents. But a baby with Edwards' syndrome has three copies of chromosome number 18, instead of two.

The presence of this extra chromosome in cells severely disrupts normal development.

Edwards' syndrome is rarely inherited and is not caused by anything the parents have done. The development of three copies of chromosome 18 usually happens at random during the formation of either the egg or sperm.

As this happens randomly, it's extremely unlikely for parents to have more than one pregnancy affected by Edwards' syndrome. However, the chance of having a baby with Edwards' syndrome does increase as the mother gets older.

Mosaic trisomy 18

Mosaic trisomy 18 can be a less severe form of Edwards' syndrome, as only some of the cells have the extra copy of chromosome 18, rather than every cell.

How severely affected the baby is depends on the number of and type of cells that have the extra chromosome. Some babies may only be mildly affected, while some can be severely disabled.

Around seven in every 10 babies born with mosaic trisomy will live for at least a year and, in rare cases, may survive into early adulthood.

Partial trisomy 18

In partial trisomy 18 only a section of the additional chromosome 18 is present in the cells, rather than a whole additional chromosome 18.

This type of Edwards' syndrome is more likely if one the parents has a minor alteration in their chromosomes, so blood samples are often requested from both parents to check for this and to help them understand the risks for future pregnancies.

How severely affected the baby is will depend on which part of chromosome 18 is present in the cells.

Symptoms of Edwards' syndrome

Babies with Edwards' syndrome can have a wide range of different problems.

Physical signs of Edwards' syndrome include:

• low birthweight
• a small, abnormally shaped head
• a small jaw and mouth
• long fingers that overlap, with underdeveloped thumbs and clenched fists
• low-set ears
• smooth feet with rounded soles
• a cleft lip and palate
• an exomphalos (where the intestines are held in a sac outside the tummy)

Babies with Edwards' syndrome also typically have:

• heart and kidney problems
• feeding problems – leading to poor growth
• breathing problems
• hernias in the wall of their stomach (where internal tissues push through a weakness in the muscle wall)
• bone abnormalities – such as a curved spine
• frequent infections of the lungs and urinary system
• a severe learning disability

Diagnosing Edwards' syndrome

During pregnancy

Pregnant women are offered screening for Edwards' syndrome between 10 and 14 weeks of pregnancy to assess the chances of their baby having the condition.

This screening test is known as the combined test, and it also screens for Down's syndrome and Patau's syndrome.

During the combined test you will have a blood test and a special ultrasound scan where the fluid at the back of the baby's neck (nuchal translucency) is measured.

Read more about screening for Edwards' syndrome at 10-14 weeks.

If the combined test shows that you have a higher risk of having a baby with Edwards' syndrome, you will be offered a diagnostic test to find out for certain if your baby has the condition.

This involves analysing a sample of your baby's cells to check if they have an extra copy of chromosome 18.

There are two different ways of getting this sample of cells – chorionic villus sampling, which collects a sample from the placenta, or amniocentesis, which collects a sample of the amniotic fluid from around your baby.

These are invasive tests that do have a risk of causing a miscarriage. Your doctor will discuss these risks with you.

Later in pregnancy, usually when you are 18-21 weeks pregnant, you will also be offered a scan that looks for physical abnormalities, known as congenital anomalies.

Read more about the mid-pregnancy scan.

A newer test has also been developed that can be performed by taking a sample of blood from the mother, at 10-12 weeks, and testing the baby's DNA that is found within it. This is known as "non-invasive prenatal testing (NIPT)" and is currently available privately, but will be offered on the NHS from 2018.

The charity Antenatal Results and Choices (ARC) has more information about NIPT.

After birth

If doctors believe a baby has Edwards' syndrome when it is born they will take a blood sample from the baby. This will be examined to see if the baby's cells have extra copies of chromosome 18.

Making a decision

If your baby is diagnosed with Edwards' syndrome during your pregnancy your doctor will talk to you about how you want to move forward. They will discuss the options of either continuing with the pregnancy or ending it with a termination, as it is such a severe condition.

This is a very difficult situation and it is normal to feel a whole range of emotions. It may help to talk to your doctor, partner, family and friends about what you are thinking and how you are feeling.

If your baby is diagnosed with Edwards' syndrome, either before birth or afterwards, you'll be offered counselling and support.

You can also contact ARC, which has information about screening tests and how you might feel if you are told your baby does have, or might have, a problem.

ARC has a helpline that can be reached on 0845 077 2290, or 020 7713 7486 from a mobile, Monday to Friday, 10am-5.30pm. The helpline is answered by trained staff, who can offer information and support.

Read more about what happens when antenatal screening finds a possible problem.

Treating Edwards' syndrome

There is no cure for Edwards' syndrome and the symptoms can be very difficult to manage. You are likely to need help from a wide range of health professionals.

Treatment will focus on immediately life-threatening issues, such as infections and heart problems. Your child may also need to be fed through a feeding tube, as feeding is often a problem.

If limb abnormalities affect your child's movements as they get older, they may benefit from supportive treatment, such as physiotherapy and occupational therapy.

Depending on your child's specific problems, they may need specialist care in hospital or a hospice, or you may be able to look after them at home with appropriate support.

Advice for carers

Caring for a child with Edwards' syndrome is mentally and physically challenging. Most carers will need social and psychological support.

Your guide to care and support provides lots of advice on how you can take time to look after yourself, including:

• keeping fit and healthy
• getting a break from caring
• getting legal support and advocacy
• taking care of your wellbeing

You can also visit the SOFT UK website for support and more information on Edwards' syndrome, and to contact other families affected by the condition.

Information about your child

If your child has Edwards' syndrome, your clinical team will pass information about them on to the National Congenital Anomaly and Rare Diseases Registration Service (NCARDRS).

This helps scientists look for better ways to prevent and treat this condition. You can opt out of the register at any time.

Find out more about the register.