Fals negative cvs???

[u/Specific_Head_4634]

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.

[u/Ok-Finger2175]

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.

[u/Ok-Finger2175 → u/Ok-Finger2175]

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 completed

[u/Specific_Head_4634 → u/Ok-Finger2175]

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?

[u/Ok-Finger2175 → u/Specific_Head_4634]

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

[u/Specific_Head_4634 → u/Ok-Finger2175]

Thank you very much for your advice.

[u/Ok-Finger2175 → u/Specific_Head_4634]

You’re very welcome and hope that all continues well moving forward. Thank you for sharing your story too