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Edwards' syndrome (trisomy 18)

What is Edwards' syndrome?

Edwards' syndrome is a serious but rare genetic condition. It is also known as trisomy 18 and occurs when there is an extra chromosome (number 18) in some, or all, of the cells in a baby's body. This severely disrupts development.

Most babies affected by Edwards' syndrome will die before or shortly after birth. Nearly three-quarters of babies with this syndrome are miscarried or stillborn.

The condition is thought to affect around 7 in every 10,000 live births in England and Wales – that's around 500 babies a year. Around half of these will die within 2 weeks. Around 1 in 12 will live to see their first birthday but will have serious disabilities. Around 1 in 10 will live until 10 years of age.

Baby girls will have higher rates of live birth than baby boys.

There are two types of Edwards' syndrome:

Full form – the more severe form of the syndrome where every cell in the body has three copies of chromosome 18, instead of two.

Mosaic trisomy 18 – a less severe form of the syndrome where the extra copy of chromosome 18 is only found in some cells. Around 5% of babies with Edwards' syndrome will have mosaic trisomy 18.

Symptoms of Edwards' syndrome

Babies with Edwards' syndrome will have a wide range of serious problems affecting nearly every organ system in the body.

Signs of Edwards' syndrome include:

  • Heart defects and kidney problems
  • Part of the intestines in a sac outside the stomach (omphalocele)
  • Hernias in the wall of the stomach
  • A small, strawberry shaped head
  • A small jaw
  • Low set ears
  • Cleft lip
  • Clenched hands
  • Smooth 'rocker bottom' feet
  • A severe learning disability.

Edwards' syndrome diagnosis and screening

Most diagnoses are made in the antenatal period.

Pregnant women are offered screening for Edwards' syndrome between 10 and 14 weeks. This is known as the combined test and involves a blood test plus a nuchal translucency ultrasound scan.

Later they are offered a mid-pregnancy (18-21 weeks) ultrasound scan that looks for physical abnormalities and rare conditions, including Edwards' syndrome.

If these tests show the chance of your baby having Edwards' syndrome is higher than 1 in 150 you will be offered more tests, either amniocentesis or chorionic villus sampling. These are invasive tests and carry a small risk of miscarriage. Fluid or tissue is removed from the amniotic sac or placenta, which can then be tested to see if there is an extra copy of chromosome 18.

There is a privately available test which can be carried out from 10 weeks of pregnancy. It involves taking a blood sample from the mother and testing the baby's DNA found within it. This is known as 'non-invasive prenatal diagnosis' NIPT. Its use is being evaluated by the NHS.

Causes of Edwards' syndrome

Edward's syndrome is a random occurrence and is not down to anything the parents may or may not have done.

Very rarely it is inherited.

The chances of having a baby with Edwards' syndrome are higher in older mums.

Treatment for Edwards' syndrome

There is no cure for Edwards' syndrome and your child's care needs will be high.

Life threatening problems will be treated first, like heart conditions, feeding problems and infections.

Depending on a child's other symptoms they will need help from a wide range of health professionals.

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WebMD Medical Reference

Medically Reviewed by Dr Rob Hicks on October 14, 2016

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