Edwards Syndrome (Trisomy 18)

Doctors can test for several serious health conditions today as a part of routine prenatal diagnostic screening. One of the more serious conditions is Edwards Syndrome, a chromosomal condition with a devastating prognosis. Edwards Syndrome is also known as Trisomy 18 Syndrome because affected babies usually have three copies of chromosome 18.

According to the Trisomy 18 Foundation, about 1 out of every 3,000 live births will be affected by Edwards Syndrome. But the incidence during pregnancy is much higher: As many as 95% of babies with trisomy 18 are either miscarried or stillborn. Trisomy 18 can even be a cause of some first-trimester miscarriages. It is not known why some babies with trisomy 18 are lost during pregnancy while others go on to be born alive.

Babies with Edwards Syndrome who do make it to birth are usually born with severe health problems, often involving malformations of the heart and other major organs. They may not be able to breathe without assistance, and they may require multiple surgeries before they can even leave the hospital. Only about 5% to 10% of babies born with Edwards Syndrome survive to their first birthday, and only a handful have survived to adulthood. Those who do survive always have severe developmental delays as well as continued fragile health.

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 some of the baby's cells are affected by trisomy 18 whereas others are not. The latter two types are rare compared to full trisomy 18. The prognosis does not differ by type.

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.

A diagnosis of trisomy 18 can only be confirmed by amniocentesis or CVS (or genetic testing after the baby's birth if the condition is not diagnosed prenatally). Screening tests such as the alphafetoprotein test cannot confirm (or entirely rule out) trisomy 18 but can merely indicate a statistical odds that the baby might have the condition. Many babies who are flagged on screening tests as having higher risk for trisomy 18 do not actually have trisomy 18.

Most of the time, trisomy 18 is a random occurrence due to problems in cell division. In rare cases, parents can be carriers for partial trisomy 18 due to a condition called balanced translocation that increases the risk that future pregnancies will be affected. 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.

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.

If you are in this position, your doctor will probably ask you to make a decision on what you want to do about the pregnancy. You can ask to speak with a genetic counselor, who can give you more information on what to expect if you choose to continue the pregnancy and how to prepare for what lies ahead. Regardless of what you choose, it is fine to grieve the loss of the baby you dreamed of when you learned you were pregnant, and it may be helpful to seek an in-person or online support group for parents who have had babies affected by Edwards Syndrome.