Fruit of the Womb
Fruit of the Womb

Chromosomal Abnormalities and Multiple Gestations - 2

…After talking with one of our genetic counselors, I went back into the room (see previous post). By this time, they had both used some tissues and were ready to talk more. They agreed to see the counselor and we walked across the hall to her office. (We are blessed with great genetic counselors). Over the course of 30-40 minutes, she explained ‘nondisjunction’ as the cause of increased risk for chromosomal abnormalities with advancing age, the actual risk for aneuploidy in midtrimester at age 40 in singleton (1/75 for Down syndrome; 1/44 for all aneuploidy) and twin pregnancies (about twice these risks that one of the babies will be abnormal in twins from different eggs), the diagnostic procedures that could be done to confirm the diagnosis, the benefits of knowing if the baby has a chromosomal abnormality with regard to decision-making during and after the pregnancy, and specific information with regard to the presumptive diagnosis of trisomy 18.

The patient was then asked if she wanted an amniocentesis and both she and her husband agreed that, based on what we had told them, they needed to know if the baby had a chromosomal problem, even though “we only want the procedure done on the baby that appeared abnormal.” (I wish I could accurately portray here the skepticism that was conveyed in the way the word “appeared” was inflected, but never being one to take away all hope, I just let it slide). I told them that under the circumstances, that was a very reasonable request. The normal ‘growth and appearance’ of the other baby probably reduced her risk for a chromosomal abnormality by as much as 90%. The procedure was then explained to them, including the small risks, and a consent was signed. As I always do under these circumstances, I made it quite clear that if the baby was lost following the amniocentesis, it would be much more likely due to the condition of the baby rather than to the procedure itself. She nodded that she understood. When asked if they had any questions, the only query was the inevitable, “I heard these things are awful…does it really hurt.” Welcoming the query, I gave her my patented reply that “it is going to be the most painful thing you have ever been through in your entire life and the large nurses in the room are here to hold you on the table.” She smiled and we did the procedure without any complications.

The amniotic fluid was sent for fetal karyotype studies by both fluorescent in situ hybridization (FISH) and routine culturing techniques. She was offered the FISH and told that a ‘presumptive diagnosis’ could be back within 48-72 hours and the routine culturing studies (results available in 10-14 days) could be used to confirm the FISH results and/or identify other chromosomal abnormalities not detected by the FISH assays; and, she readily accepted this approach. We would notify her directly as soon as any results were back and arrange for her to return to discuss the findings and options for follow-up depending on the diagnosis and her own needs.

A few days later, unfortunately, but as expected, the baby’s karyotype by FISH came back as 47XY,+18 (trisomy 18). When she was called, her immediate response was, “Some friends told me the FISH has lots of false-positives, so the baby could still be all right, right? Don’t we have to wait for the final results of the cultures?” Again, not to mince words, I told her that it was very unlikely the cultures would change the FISH results. In fact in 20 years, I have not seen a single FISH diagnosis of aneuploidy be overturned by the culture technique (although I have seen ‘negative’ FISH studies in circumstances where the final results demonstrated a chromosomal abnormality not included in the FISH profile). The silence that followed was deafening, and the crying that followed that was heartbreaking, but when she finally asked between tears, “Where do we go from here?,” I knew we were going to be alright. “Why don’t you come back to talk with us when you are ready; we’ll work you in on a moment’s notice if necessary…”
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