Diagnosis and Prognosis of Edwards Syndrome

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One of the more serious health conditions checked in routine prenatal diagnostic screening is Edwards Syndrome, a chromosomal condition with a devastating prognosis. Edwards Syndrome is also known as trisomy 18 syndrome because there are three copies of chromosome 18.


Edwards Syndrome is occurs in 1 out of every 4,000 births. However, the incidence during pregnancy is much higher because it may be unrecognized. Many women whose fetus has trisomy 18 have a miscarriage or stillbirth.

Sadly, the outcomes for babies born with Edwards Syndrome are not good, including:

  • Half of the infants do not survive beyond the first week of life.
  • About 90% to 95% of children will die before their first birthday. 
  • Some children survive to the teenage years, but with serious medical and developmental problems.


The most common form of Edwards Syndrome is full trisomy 18, meaning the baby has three full copies of the 18th chromosome instead of two. It is also possible to have partial trisomy 18, in which there are two full copies of chromosome 18 and also an additional partial copy. Still another type is mosaic trisomy 18, meaning there is an effect on some, but not all, cells.

The latter two types are rare compared to full trisomy 18. Patients with mosaic trisomy 18 may be severely affected or not. In fact, it's possible for a patient to have mosaic trisomy 18 and not know it until he or she has a baby diagnosed with trisomy 18.

Causes and Risk Factors

The extra copy of chromosome 18 is already present at the time of fertilization and results from random errors in cell division. Trisomy 18 can occur in parents of all age groups, but the risk is highest when moms are older than 35. Although most trisomy 18 is due to random errors, partial trisomy 18 can be inherited.

How Is It Diagnosed?

An amniocentesis, chorionic villus sampling, or first trimester screening with blood testing and ultrasound evaluation of the nuchal fold can test for Edwards Syndrome. Trisomy 18 is usually diagnosed before a baby is born by the combination of the mother's age, blood tests, and/or evidence of abnormalities on a sonogram.

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 for partial trisomy 18 due to a condition called balanced translocation that increases the risk for future pregnancies.

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

Facing an Edwards Syndrome Diagnosis

An Edwards Syndrome diagnosis is devastating news. Many parents choose to terminate their pregnancies after receiving a confirmation that the baby definitely has trisomy 18, given the high risk of severe health problems and the low odds of the baby surviving infancy.

Others decide to continue the pregnancy anyway, either because of beliefs against abortion or because of a mindset that they want to treasure the time with the baby even if it is short. There is no "correct" choice for what to do in this situation. Parents facing this diagnosis should do what feels right for them.

2 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Cereda A, Carey JC. The trisomy 18 syndromeOrphanet J Rare Dis. 2012;7:81. doi:10.1186/1750-1172-7-81

  2. U.S. National Library of Medicine. Genetics Home Reference: Trisomy 18.

By Krissi Danielsson
Krissi Danielsson, MD is a doctor of family medicine and an advocate for those who have experienced miscarriage.