Finn’s Diagnosis

Some of you may know that I have felt doubt from the beginning about Finn’s post-death diagnosis of full Trisomy 9. That is both due to his lack of exhibiting signs of the condition, and the assumption that was made when he was diagnosed. I had a very normal pregnancy with Finn. No red flags were ever raised. The anatomy scan at 18 weeks was perfect, with absolutely no concerns about his growth and development. He was declared a healthy baby boy. His growth must have dropped off suddenly, rather than him measuring small all along. As I remember, he always measured right on target until my last check-up at 33 weeks, when my fundal height measured 32 weeks. My doctor had no concerns at the time. I was told he measured in range, and to schedule my next appointment in two weeks. At 35 weeks, the day before my next appointment was scheduled, his heart stopped beating. At 3 lbs, 11 oz and 16 3/4 inches, Finn was only in the 2nd percentile for weight for his gestational age. At birth, he measured the size of an average 32 week baby. Since he measured the same size at birth as he did at my last appointment, the logical conclusion is that he didn’t grow after that. This is important because Trisomy babies tend to be smaller than average from early on in pregnancy.

With nearly every Trisomy pregnancy I’ve learned about, there were multiple severe and obvious abnormalities identified during the anatomy scan. These abnormalities usually prompt doctors to do an amniocentesis or CVS, which then comes back positive for Trisomy. It’s a very common theme in Trisomy-related discussion groups. Most Trisomy parents knew at least a few months before birth that their babies would not survive long after birth, if not be stillborn. Trisomy babies also have very distinct physical markers, which vary depending on which extra chromosome they have and how it manifests. The lower the number of Trisomy, the more severely it affects the body and the lower the survival rate. Severe heart, brain, and organ abnormalities are common, but none were ever found with Finn. It is not unusual for Trisomy children to have small skulls, cleft lips, irregular facial features, and overlapping fingers. Finn had none of these physical markers.

At the time Finn died, we had no idea what had gone wrong. Sonograms were done after Finn’s death, but before he was born, to try to identify any abnormalities. An autopsy was performed on his body, but came back with no abnormalities, other than he was small for gestational age and the placenta was small as well. We also had a chromosomal micro-array test (CMA) done to check for chromosomal abnormalities. A sample of fetal-facing placental cells was sent for testing, meaning all the cells tested were from the placenta; none of those cells came from Finn’s actual body. Taking the sample this way is standard hospital procedure from what I understand. The CMA test came back positive for full Trisomy 9. Our geneticist told us Trisomy 9 was absolutely fatal, that it causes severe deformities, most babies with it are miscarried in the first trimester, and Finn would have died shortly after birth if he hadn’t been stillborn. I remember my initial reaction was confusion. How did that describe my baby when it sounded nothing like him? Did they mix up the results with some other person? I just went through an entire uneventful pregnancy and was told I was carrying a healthy baby,  and yet my baby supposedly had a condition that typically causes physical abnormalities severe enough to not survive the first trimester? I never doubted the accuracy of the test results, but I always had trouble reconciling how that diagnosis fit my seemingly healthy baby with no determinable external or internal abnormalities. I felt even more out of place as I spoke with other Trisomy parents. Finn’s story didn’t fit with theirs at all.

A few months after receiving that diagnosis, through an online stillbirth support group, I came across another angel mom’s story . She described how her son’s placenta tested positive for Trisomy 13, but he had normal chromosomes. After talking to her, I found out her son began measuring small at the beginning of the third trimester. The doctors decided to do a CVS to see if they could figure out what was wrong. The cells they retrieved from the placenta tested positive for Trisomy 13, so they assumed he had Trisomy 13 and told her that her son wasn’t going to survive. Most often, the cells in the placenta match the fetal cells so this assumption usually holds true. However, after the doctor watched her baby open and close his hands on a sonogram, which is something a Trisomy 13 baby shouldn’t be able to do, they decided to test his cells, and they found he had normal chromosomes, or Confined Placental Mosaicism. It is a condition in which the placenta is chromosomally abnormal but the baby is chromosomally normal. It is rare and only occurs 1-2% of pregnancies. It happens when either abnormal cells are isolated to the placenta during early pregnancy in a biological attempt to save the baby, or a random cell mutation occurs in the placental cells after the pregnancy cells separate into the fetus and placenta and that mutation continues to replicate such that the placenta is made of abnormal cells. This condition can cause IUGR (growth restriction) that sometimes results in stillbirth. The placenta is abnormal and can’t supply the needed nutrients and oxygen, especially as the pregnancy progresses into the third trimester and demands on the placenta are much higher. Unfortunately doctors did not deliver this mom’s son soon enough and he died in the womb. He was born at 32 weeks measuring in the 1st percentile for weight.

I also met a mom of a full Trisomy 9 baby who died shortly after birth. She is the only mom I’ve talked to with a full Trisomy 9 baby, which gives you an idea of just how rare it is. She said it was very obvious something was wrong at the anatomy scan. Her baby had serious heart and brain abnormalities. A whole section of his brain was missing, as were the connections between the different parts of his brain. He didn’t know how to swallow, resulting in excess amniotic fluid build-up during her pregnancy. As a result, she measured several weeks ahead. After talking with her, I feel even more strongly that mine was a case of Confined Placental Mosaicism rather than fetal chromosomal abnormality. After finding out about Confined Placental Mosaicism, I asked our geneticist if this was was a possibility in Finn’s case, and she agreed it was possible, although rare, and said the pregnancy would have been severely compromised. Since Finn’s actual cells were never tested, we can never know for sure. When I first learned of this possibility,  I was frustrated and overcome with grief again, because it meant he could have lived had he been delivered soon enough. However, now that I have come to terms with it, I’m actually more able to accept Finn’s death and the circumstances surrounding  it, because it actually makes sense. It fits.

Additional information:

Wikipedia – Confined Placental Mosaicism

Confined placental mosaicism

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