u/SofieGirlsMama

Hi everyone! I (26 YOF) am currently 17 weeks pregnant my second baby boy and wanted to ask if anyone here has seen a similar circumstance to mine. My first boy is 12 months old and completely healthy.

My NIPT LabCorp blood draw was at 10 weeks 2 days pregnant and the fetal fraction was 20%. PPV 66%. The results were flagged as abnormal for T21 (Down Syndrome) but it was considered a “low-mosaic” pattern, so they believe it may be confined placental mosaicism or I had vanishing twin syndrome. Or my baby could have low mosaic T21 which comprises roughly 1-2% of all babies diagnosed with T21.

The genetic counselor told me that the cut off for LabCorp even flagging this as a high risk is 19% of the cells showing an extra copy of chromosome 21. And my sample had 22% of the cells affected. That’s why she suspected this result may not truly represent fetal mosaicism and may be resulting from some other source.

At 13 weeks I had an early anatomy ultrasound with no soft markers for T21. At 16 weeks I had another ultrasound revealing an echogenic bowel, but it was otherwise a normal ultrasound with no other soft markers.

I had an amniocentesis at 16 weeks. FISH results came back completely normal. All 50/50 cells tested were negative for anomalies of chromosome X, Y, 13, 18, and 21. I’m still waiting the karyotype and microarray results.

Unfortunately, the hospital messaged me saying they had enough fetal DNA in the amnio sample to run the FISH and karyotype, but not the uncultured SNP microarray. They said for the microarray, the cells would need to be cultured but that could potentially skew the results in the case of mosaicism. They also told me it’s going to add 4-6 weeks to the results timeline which is frustrating.

Has anyone seen FISH results be completely normal for T21 but ended up having a low level mosaic result in the karyotype or microarray? My genetic counselor said it’s uncommon but not unheard of for this to happen after a normal FISH. Anyone know the stats on that?

Hi everyone! I (26 YOF) am currently 17 weeks pregnant my second baby boy and wanted to share my story and ask if anyone else has gone through something similar. My first boy is 12 months old and completely healthy.

My NIPT LabCorp blood draw was at 10 weeks 2 days pregnant and the fetal fraction was 20%. PPV 66%. The results were flagged as abnormal for T21 (Down Syndrome) but it was considered a “low-mosaic” pattern, so they believe it may be confined placental mosaicism or I had vanishing twin syndrome. Or my baby could have low mosaic T21 which comprises roughly 1-2% of all babies diagnosed with T21.

The genetic counselor told me that the cut off for LabCorp even flagging this as a high risk is 19% of the cells showing an extra copy of chromosome 21. And my sample had 22% of the cells affected. That’s why she suspected this result may not truly represent fetal mosaicism and may be resulting from some other source.

At 13 weeks I had an early anatomy ultrasound with no soft markers for T21. At 16 weeks I had another ultrasound revealing an echogenic bowel, but it was otherwise a normal ultrasound with no other soft markers.

I had an amniocentesis at 16 weeks. FISH results came back completely normal. All 50/50 cells tested were negative for anomalies of chromosome X, Y, 13, 18, and 21. I’m still waiting the karyotype and microarray results.

Unfortunately, the hospital messaged me saying they had enough fetal DNA in the amnio sample to run the FISH and karyotype, but not the uncultured SNP microarray. They said for the microarray, the cells would need to be cultured but that could potentially skew the results in the case of mosaicism. They also told me it’s going to add 4-6 weeks to the results timeline which is frustrating.

Does anyone have experience with FISH results being completely normal for T21 but ended up having a low level mosaic result in the karyotype or microarray? My genetic counselor said it’s uncommon but not unheard of for this to happen after a normal FISH.

Thank you in advance!

Hey everyone! I’m a 26 year old second time mom to an 11 month old perfectly healthy baby boy. I wanted to share where I’m currently sitting after receiving NIPT results.

LabCorp blood draw on 5/13 at 10w2d and I received a call from my midwife with results two days ago. Fetal fraction 20%.

The results were flagged as abnormal for Trisomy 21 (Down Syndrome) but it was considered “low-mosaic”, so they believe the Trisomy 21 cells may be originating from my placenta or I have vanishing twin syndrome. It’s a possibility that baby is not affected whatsoever.

The genetic counselor told me today that the cut off for LabCorp flagging this as an abnormal result is 19% of the cells in the placenta having an extra copy of chromosome 21. And my placenta had 22% of the cells affected. So my placenta contained only a 3% higher level of affected cells than the cutoff for LabCorp even flagging this as an abnormal result.

Usually with the typical Down syndrome pattern they’d expect 99% of the cells affected, so she thinks it’s super unlikely that the baby actually has Down Syndrome. The genetic counselor also said the risk is super low given I’m only 26 years old and the risk of having a baby with Down syndrome is about 1 in 1,250 at my age.

They’re sending me to maternal fetal medicine for a detailed anatomy ultrasound on June 1st, and if the anatomy scan is normal, that’s an even stronger sign that baby doesn’t have Down syndrome.

I have to decide whether I want an amniocentesis at 16 weeks along to determine whether baby is affected. But I know that test carries risks in itself…

Anyone else been in a similar situation as me? It seems like I’m an enigma, as mosaicism is very rare and only affects 1-2% of all Down syndrome cases…

I’m truly holding onto hope that everything is okay and baby is healthy. 😭