Edwards' syndrome (trisomy 18)

5 min read

Edwards' syndrome, also known as trisomy 18, is a genetic condition. Nearly three-quarters of babies with the syndrome are miscarried or stillborn and the babies who survive beyond one year will have a developmental disability.

In almost all cases of Edward's syndrome, the child develops three copies of chromosome 18 in each cell of their body, instead of the usual two.

Normally, each cell in the body contains 23 pairs of chromosomes, which carry the genes you inherit from your parents.

Learn more about genetics

The extra genetic material in Edward's syndrome disrupts the baby's normal course of development.

Babies with Edward's syndrome will have grown slowly in the womb and will have a low birthweight. Doctors may suspect that a baby has Edward's syndrome just by their characteristic features (see below), although the disease must be confirmed with genetic tests.

What are the features and symptoms of Edwards' syndrome?

Physical signs of Edwards' syndrome include:

  • a small, abnormally shaped head
  • a small jaw and mouth
  • long fingers that overlap, with short fingernails and clenched fists
  • low-set ears
  • smooth 'rocker bottom' feet (with a rounded base)

Babies with Edwards' syndrome also typically have:

  • heart and kidney problems
  • feeding problems in infancy, leading to poor growth
  • breathing problems
  • hernias in the wall of their tummy (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

How serious is Edwards' syndrome?

Sadly, most babies with Edwards' syndrome are miscarried or stillborn.

A third of babies born alive will die within a month of birth because of life-threatening medical problems.

Only 5-10% of babies with full Edwards' syndrome survive beyond one year, and will live with severe disabilities. Those with mosaic and partial forms (see below) often survive to adulthood.

How does Edwards' syndrome happen?

Edwards' syndrome is rarely inherited.

Trisomy 18 (developing three copies of chromosome 18) usually happens randomly during the formation of eggs and sperm. There is an error in the division of cells, and the extra chromosome is either in the egg cell produced by the mother or in the sperm cell produced by the father.

Because this happens randomly, it's extremely unlikely for parents to have more than one pregnancy affected by Edward's syndrome.

The disease affects three times more females than males.

Types of Edwards' syndrome

Full form

Approximately 94% of babies with Edward's syndrome will have the full form of the disease, where every cell in their body has three copies of chromosome 18 instead of two. Most babies with the full form will die before infancy.

Mosaic trisomy 18

About 5% of babies with Edward's syndrome will have the extra copy of chromsome 18 in only some of their body cells. This less severe form of the disease is known as mosaic trisomy 18.

The severity of mosaic trisomy 18 depends on the type and number of cells that have the extra chromosome. Some babies may only be mildly affected, while some can be severely disabled.

Partial trisomy 18

Babies with the partial form of the disease will have an extra copy of only part of chromosome 18. The severity of partial trisomy 18 depends on the amount of chromosome material that is triplicated.

Some babies may only be mildly affected, while some can be severely disabled.

Babies with the mosaic or partial form of the disease may survive into adulthood, although this is unusual.

How common is Edwards' syndrome?

Edward's syndrome affects around 1 in 3,000-5,000 live births. The chance of having a baby with Edward's syndrome increases with the mother's age.

Testing for Edwards' syndrome during pregnancy

Edward's syndrome is often detected during pregnancy and some parents opt to terminate the pregnancy.

In most cases (90%), signs that the baby may have Edward's syndrome are picked up at the routine 18-20 week ultrasound fetal anomaly scan.

The blood test for Down's syndrome can also suggest that the condition is present.

It is confirmed by carrying out

chorionic villus sampling (CVS)
– invasive tests carried out during pregnancy to detect whether the unborn baby could develop, or has developed, an abnormality or serious health condition. The above links will take you to more information on these tests.

Is there any treatment for 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 different health professionals.

Your child may benefit from physiotherapy and occupational therapy, if limb abnormalities affect their movements. They may need to be fed through a feeding tube.

As a parent carer, it's important that you look after your own health and wellbeing, too. The box on this page provides links to further information that may help you.

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.