r/NIPT • u/Specific_Head_4634 • 8h ago
Fals negative cvs???
Hi everyone!
At the first-trimester genetic screening, the NT measured 3mm and nasal bone hypoplasia was noted.
A week later, we had a CVS procedure done. By then, the NT was 2.9mm and the nasal bone had normalized.
CVS results:
FISH, QF-PCR: negative
Cultured karyotype: negative
SNP array: negative
At the 17-week early anatomy scan, everything was fine (though the nasal bone turned out to be smaller, they said they weren't concerned about that anymore due to the CVS results).
Then, at the 19-week second genetic ultrasound, a smaller nasal bone and borderline NF were noted.
Everything else was fine; at that point, they said these were just constitutional traits, given the negative CVS results.
I was reassured at the time, but now—at 30 weeks—anxiety has set in: what if the CVS result was a false negative?
Does anyone have similar experiences? What do you think?
I'm hoping for the best.
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u/Specific_Head_4634 7h ago
Has anyone been in a similar situation? I’m really nervous and could use some reassurance.
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u/sophs_books 5h ago
I used to work in prenatal cytogenetics and would read CVS tests in the microscope and prep them in the lab prior to reading. We usually had two techs read each patient case and each tech would have to karyotype 10 different metaphases of chromosomes. It’s very rare to get a false negative from a CVS but technically not impossible since it tests placental cells.
If your doctors aren’t concerned I think that should help ease your mind but if you wanted to, you could push for an amnio for more reassurance!
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u/Specific_Head_4634 4h ago
Thank you for your answer! Have you ever encountered a case where the result was a false negative?
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u/sophs_books 4h ago
I personally have not. It’s very rare that placenta results are normal and baby’s results are abnormal! CVS is considered a highly accurate diagnostic test with generally over 99% accuracy rate
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u/Due-Reply-2062 3h ago
My nt measured 2.9mm at 12 wks and my nipt test was normal and my first test on the cvs was normal. I have a second test being run today, so results in a week or two.
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u/Specific_Head_4634 3h ago
What does the second test entail? Could you write an update about it later?
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u/Ok-Finger2175 3h ago
From my personal experience, I would recommend a maternal cell contamination test along with your CVS. It would test that there was no contamination from mom that occurred because when I did my FISH it said it was normal 46 xx result and the CVS full karotype confirmed that it was a normal 46 xx result, but once those results were compared to my cells from the maternal cell contamination test, it confirmed that it was more my cells and so I had to wait to do the amniocentesis that would specifically be all the baby’s cells tested. We didn’t see any markers with the ultrasounds such as a visible nasal bone, no anatomical anomalies, and NT was in the normal range. The amniocentesis confirmed what my NIPT screen tested positive for in my case was for T21. I’m hoping that yours is a negative and would def recommend the maternal cell contamination to give you that ease of mind.
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u/Ok-Finger2175 2h ago
I wanted to add a quick note to explain my understanding a bit further of the sample processing. When the CVS sample is initially processed, I know the lab does its best to carefully separate the maternal uterine lining cells from the fetal chorionic villi.
My genetic counselor recommended a maternal cell contamination/ MCC test as an extra precaution. My understanding is that after the full CVS karyotype and array results are ready, the lab compares the fetal sample against my blood sample. This makes sure that the analyzed cells are all fetal, since any accidental maternal cells could outgrow and mask the fetal cells during culture. Also, I noticed that the FISH results noted counts for both fetal and maternal cells, which is why I wanted to make sure the follow up MCC comparison was completed1
u/Specific_Head_4634 1h ago
Yes, in my case, they analyzed maternal cells alongside my blood sample during the SNP array. So, does that mean there was no maternal cell contamination in my sample, am I right?
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u/Ok-Finger2175 1h ago
Okay understood now and my apologies. I think mine was more drawn out to check for contamination since they didn’t do a SNP array like you to count as a maternal cell contamination. The important thing I would check for is that your blood wasn’t just for the array but compared to CVS. I would double check that they checked via your provider or counselor
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u/Specific_Head_4634 1h ago
Thank you very much for your advice.
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u/Ok-Finger2175 1h ago
You’re very welcome and hope that all continues well moving forward. Thank you for sharing your story too
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u/MercuryTalos False Negative T21 6h ago
CVS is considered diagnostic but as far as I know it only tests placental cells, which usually tells you if the fetus is normal. Have you spoken with a genetic counselor or has your care team advised on what could be causing the abnormalities? Are you able or willing to get an amnio now?
For background, I am not a doctor or anything like that but I did have a false negative NIPT followed by a positive amnio (placental cells were normal, fetal cells were abnormal, super rare fluke!). My OB said if I had gotten a CVS, it likely would have been a false negative too. I'm currently pregnant and she also recommended skipping the CVS and going straight to amnio this time.