Trisomy 18: Definition, Statistics, Symptoms, Types, Causes, Diagnosis and Treatment

It is a chromosomal condition with a devastating prognosis.

One of the most severe health conditions controlled in routine prenatal diagnostic screening is Edwards Syndrome.

Edwards Syndrome is also known as Trisomy 18 Syndrome because there are three copies of chromosome 18.


Edwards syndrome occurs in 1 in 6,000 live births and is three times more common in girls, according to the National Institutes of Health (NIH).

However, the incidence during pregnancy is much higher because as many as 95 percent of women whose fetus has trisomy 18 have a miscarriage or stillbirth.


  • Half of the babies do not survive beyond the first week of life.
  • Nine out of 10 children will die before their first birthday.
  • Some children persist into adolescence but with severe developmental and medical problems.


The most common form of Edwards syndrome is complete trisomy 18, which means that the baby has three full copies of chromosome 18 instead of two.

It is also possible to have partial trisomy 18, in which there are two complete copies of chromosome 18 and one additional partial copy.


Yet another type is mosaic trisomy 18, which means that some cells have an effect, but not all. The last two types are rare compared to complete trisomy 18.

The prognosis does not differ by type.

Causes and risk factors

The extra copy of chromosome 18 is already present at fertilization and is the result of random errors in cell division.

Trisomy 18 can occur in fathers of all ages, but the risk is higher when mothers are older than 35.

What is the treatment for trisomy 18?

Treatment of children with Edwards syndrome depends on the severity of the findings.

There is no definitive treatment for children with trisomy 18, and there are ethical issues surrounding the treatment of these newborns.

This is due to the high mortality rate and difficulty predicting which babies will live beyond the first year of life.

Many of these babies’ leading cause of death is sudden death due to neurological instability, heart failure, and respiratory failure.

For infants diagnosed with incomplete trisomy 18 or mosaic trisomy 18, treatment focuses on addressing the abnormalities present as they have such a variable prognosis.


An amniocentesis or chorionic villus sampling can test for Edward Syndrome.

The alpha-fetoprotein test cannot confirm (or completely rule out) trisomy 18, but it may indicate statistical odds that the baby may have the condition.

Some tests are less accurate than others. Genetic testing is an evolving field, and newer and more accurate tests will be on the horizon.

This trisomy 18 diagnosis is essential to better prepare parents and caregivers due to the high risk of stillbirth and early postnatal death.

Risk of recurrence

Most of the time, trisomy 18 is a random occurrence due to problems in cell division.

In rare cases, parents are carriers of partial trisomy 18 due to a condition called balanced translocation that increases the risk of future pregnancies.

If there is a possibility that you are a carrier, your doctor may refer you to a genetic counselor to discuss your options. But most parents who have babies with trisomy 18 are not carriers.

We are faced with a diagnosis of Edwards Syndrome.

A diagnosis of Edwards Syndrome is devastating news.

Many parents choose to terminate their pregnancies after confirmation that the baby has trisomy 18.

Given the high risk of severe health problems and the baby’s low chances of surviving infancy, this is an increased risk of severe health problems.

Others decide to continue the pregnancy anyway, either due to anti-abortion beliefs or a mindset that they want to treasure the time with the baby, even if it is short.

There is no “right” choice for what to do in this situation. Parents facing this diagnosis should do whatever feels right for them.