About trisomy 18

Trisomy 18, or Edwards syndrome, happens when a baby’s cells have three copies of chromosome 18, rather than the usual two. The extra chromosome 18 causes severe intellectual disability and physical abnormalities.

For example, a baby born with trisomy 18 is usually underweight. Other distinguishable features include a small head and jaw, low-set ears and clenched hands.

The baby’s internal organs are often affected too, with abnormalities in the heart, lungs, diaphragm, blood vessels, gut, bones and kidneys.

Other problems can include difficulty with seeing, hearing and feeding.

The way a child is affected by trisomy 18 depends on whether all of the child’s cells contain three copies of chromosome 18, or only some of their cells. Some children might have only a few features of the condition, and other children might have many.

Most babies born with trisomy 18 don’t live beyond a week. A small percentage survive their first year and beyond.

Trisomy 18 affects both boys and girls but is more common in girls.

Causes of trisomy 18

Trisomy 18, or Edwards syndrome, is most often caused by a random error in the formation of a parent’s eggs or sperm.

Less often, this error occurs after conception, while the baby is still developing in the womb.

The older a mother is when she gets pregnant, the higher her chances of having a baby with trisomy 18.

If you have one baby with trisomy 18, your chance of having another baby with the syndrome is usually very low. But this depends on the type of condition your child has. Genetic testing can give you more information about this.

For normal human development, we need 46 chromosomes (23 pairs carrying genetic material from each parent) in all of the cells in our bodies. Chromosome abnormalities are when there are missing or extra chromosomes or changes in the structure or arrangement of the chromosomes.

Diagnosis of trisomy 18

Trisomy 18, or Edwards syndrome, is diagnosed with genetic tests.

Some tests can be done before birth. Other tests can be done after the baby is born.

Support and treatment

There is no cure for trisomy 18, or Edwards syndrome.

Doctors and parents often have to make difficult decisions about treatment. Many parents need to make a very difficult choice between making their baby comfortable and prolonging life through invasive surgery.

If your baby is diagnosed with trisomy 18, or Edwards syndrome, before or after birth, the following professionals might be able to help you: