What IS Trisomy 18 (Edwards Syndrome)?

We had nearly an hour-long consultation with a genetic counselor just before our ultrasound. Of course, after receiving the phone call from my doctor 4 days prior, we had immediately done some research on Edwards Syndrome. The analysis was pretty grim. I read enough to see that the studies on survival rates show an extremely high mortality rate either before or soon after birth for children with Trisomy 18. That was all the information I could handle during those days leading up to the ultrasound...one bridge at a time.

As you may perhaps surmise from the name of the condition, there is extra genetic material in the 18th chromosome that can cause a wide range of developmental problems. Our counselor gave us the following list of specific things the doctor would be looking for in our ultrasound:

• Heart defects, such as:

1. VSD (Ventricular Septal Defect): a hole between the lower chambers
2. ASD (Atrial Septal Defect): a hole between the upper chambers
3. Coarctation of the aorta: a narrowing of the exit vessel from the heart

• Kidney problems
• Part of the intestinal tract is outside the stomach (omphalocele)
• The esophagus doesn’t connect to the stomach (esophageal artesia)
• Excess amniotic fluid (polyhydramnios)
• Clenched hands
• Pocket of fluid on the brain (choroid plexus cysts)
• Rocker bottom feet
• Delayed growth
• Small jaw (mycrognathia)
• Small head (microcephaly)
• Low-set ears
• Strawberry-shaped head
• Severe developmental delays
• Umbilical or inguinal hernia

Among other things, our discussion also included information about how the quad screen blood test works as well as how Trisomy 18 was determined to be the risk factor for our baby as opposed to other genetic issues. It turned out to be a good biology lesson for all of three of us--Charis, our oldest daughter, had chosen to accompany us to the ultrasound. (I gave her the option since she has attended nearly every ultrasound we have ever had done...she loves seeing the babies in my womb and being the first to know their gender!)

Along with all of this, we learned more about our post-ultrasound options...what we might choose to do if the ultrasound findings were or were not clear. Basically, there were two things that could give us more specific information:

1. A blood test that would check specifically for chromosomes. This would give us results with 99% accuracy...however, there is the chance for both false positive and false negative results.
2. An amniocentesis. Based on an experience I had had 13 years prior with our third child, I was leery of getting an amnio because of the information I had received at that time, which seemed to indicate that an amnio would actually increase my chances of miscarrying the baby. The question we looked at was...does the amnio itself increase the risk of losing a baby, or is it perhaps the fact that most amnios are done during pregnancies with complications to begin with?

Armed with more information than we perhaps wanted, we decided on our own, in the counselor's office as she went to finish some paperwork, that if the ultrasound showed specific concerns, we would elect to have an amnio done immediately afterward. If the ultrasound seemed to indicate that all was well, we would go ahead and do a blood test on me just in case.

And then it was time. We followed the counselor to our ultrasound room where the tech was preparing for us.