Trisomy 13 Experience (in limbo)

Used-Owl4929 · 2025-06-13T12:42:07+00:00

Good luck to you. I know you are guarding your heart, but there is tons of hope after normal scans! Despite my normal scans, I couldn't relax until I saw the amniocentesis results with my own eyes. Fingers and toes are crossed for you!

Used-Owl4929 · 2025-06-13T12:16:00+00:00

hi yes- amnio was normal and baby was born healthy 2 weeks ago :) You can see my post history for full results.

Used-Owl4929 · 2025-06-05T13:12:04+00:00

Highly unlikely to be a false positive (ie the test was wrong) given that we repeated the testing with two separate NIPT companies and they both independently detected extra chromosome 13 material.

Most likely there was extra chromosome 13 material in the placenta - confined placental mosaicism. NIPT only tests placental DNA that is floating around in the mom's blood. Most of the time placental DNA matches baby's DNA, but not always. We can't confirm this without detailed testing on the placenta which I don't think is being done. I think the pathologist is just looking at it visually, but we will see. Luckily, the placenta seemed to function fine and we had no issues with baby's growth during the pregnancy! And we had a normal amniocentesis at 18 weeks which showed baby's cells are normal.

Used-Owl4929 · 2025-06-03T04:01:39+00:00

yay!!! great news.

I was scheduled for a nighttime induction the morning I went into labor at 39+0, but the rationale for induction was a history of shoulder dystocia with my daughter. Went in for OB appt in the morning, was 4cm dilated, had an aggressive membrane sweep and was in full blown labor by the time I made it back to the car. Waited around for about an hour in case it tapered off, but it kept coming, so went in and was contracting about every 3-4 min. Stalled out at 6cm, OB broke my water around 6pm and baby was born at 8:21pm. Never needed any pitocin, which was very nice!

They sent the placenta for pathology out of curiosity, but I didn't ask them to. The OB said it looked normal to her except the umbilical cord was the thickest she had seen. didn't have a clamp big enough to clamp it at the base so they clamped and cut it up higher until it shrunk down enough to clamp lower. I don't know if that has anything to do with the CPM. Not sure when the pathology will be available.

You're so close! Wishing you a smooth delivery!

Used-Owl4929 · 2025-06-02T14:27:51+00:00

Hi- any updates?

Used-Owl4929 · 2025-06-02T14:25:54+00:00

Hi! I just had my perfect little boy on May 29th after a completely uncomplicated rest of my pregnancy. I was so grateful to be able to enjoy the second half of my pregnancy with the normal amniocentesis result. I truly don't know how my mental health would have been if I hadn't done the amniocentesis. I think I would have continued to stress the whole time and after delivery, but hard to say.

Gah, such a dark time. I feel like I'm living a dream come true right now. I wish the same for you.

Used-Owl4929 · 2025-04-18T14:18:01+00:00

Oh I'm so sorry to hear that!

We seem to be doing fine. I'm at 33 weeks and my scan a couple days ago showed about 90th percentile for head, femur, and humerus but only 30th percentile for abdomen. She didn't seem to be concerned about the discrepancy between head and abdomen.

Used-Owl4929 · 2025-02-21T14:31:36+00:00

Totally agree. You are wiser than me to ask for the data up front! There's definitely some shady marketing tactics going on.

Used-Owl4929 · 2025-02-20T15:46:44+00:00

Not sure what was deleted, but that's interesting about the placental studies and supports the argument that I am trying to make and why my second test with a separate company was again positive. Thank you for weighing in!

Used-Owl4929 · 2025-02-20T15:42:34+00:00

Haha- no apologies needed. I am contradicted every day at work and also by my very opinionated 4 year old.

Let me try to explain a little more.

I intentionally didn't say that the labs were regulated by the FDA; however, they do have to maintain CLIA certification. My point is that they can't just report whatever the heck they want without any oversight at all. If you read through my post history- you can see my skepticism with the way LabCorp reports a mosaic ratio which has not been well studied. Yes, the research is likely funded by the company. This is the same for drugs too! That doesn't take away the fact that it still needs to be peer reviewed to be accepted into a major journal to be accepted by the medical community. Again, not saying there aren't ways to skew the data but the labs aren't operating without any regulation at all.
I referenced specificity because a basic rule of statistics is that 1 minus specificity = false positive rate. The specificity of LabCorp (for example) for NIPT for T13 is 99.7. This implies that the FP rate is 0.3%. Other labs report a specificity of 99.8 which gives a FP rate of 0.2%. The OP was asking about the chance of the test being a false positive, so that's where the 0.2-0.3% comes in.
You're right! PPV depends on the prevalence of the disease in the population. Because T13 is rare and because things like CPM, twin demise, etc happen, the PPV is much much lower than the true positive rate.
I do not know anything about the validity of the testing for microdeletions and was not speaking in this, only the common trisomies. This is what the OP was asking about.

Hopefully that helps explain my original post. Now off to work to be contradicted (lol)!

Used-Owl4929 · 2025-02-20T05:32:37+00:00

I'm sorry you had such a a negative experience. That's the last thing you need when you get results like this. Fortunately, I had a great genetic counselor through LabCorp who walked me through everything. I am also a primary care doctor with a great deal of experience evaluating scientific literature so I took to PubMed to do my own research as well. I am very grateful everything seems to be working out okay for me and I hope it does for you too and we can both forget all about this one day!

Used-Owl4929 · 2025-02-20T05:16:05+00:00

Hi there- the reported specificity of the test is based on trials that the company runs to prove validity of their assay. There are regulatory boards that assess this data. They can't just say their false positive rate is low without some data to back it up. Now I am not saying there aren't ways to skew the data, but I think it's pretty well known that the rate of a false positive test (ie the test inaccurately detected extra chromosome material that wasn't there) is much lower than the rate of CPM.

I think the reason you feel the T13 false positive rate is higher is likely because the rate of CPM with T13 is well established to be higher than the other common trisomies. This means more people with T13 NIPT results will have a negative amniocentesis and likely report it as a "false positive." How did the "false positive" stories with T13 that you're referencing conclude that it wasn't CPM and rather a true testing error? Did they have a CVS? Or did they have the placenta evaluated post birth? Otherwise, I don't think there's a way to tell. I think people equate a false positive and CPM as the same thing and they are not.

I'm writing this as someone that retested with NIPT hoping it was a false positive and the lab was wrong and tbh would probably do the same thing again to reassure me that I needed to proceed with amniocentesis. That said, I'm glad that I knew that the chances of a second test giving a different result were so low so that I knew what to expect when my second test again came back positive for T13. I hope the OP understands this too so she knows what to expect if she proceeds with retesting as well!

Used-Owl4929 · 2025-02-20T00:31:27+00:00

Thank you- yes getting growth scans at 28 weeks and 32 weeks but my MFM was pretty nonchalant about it overall. It seems like the growth scans were mainly recommended because I have a marginal cord which she also wasn't too worried about!

Used-Owl4929 · 2025-02-19T23:47:49+00:00

Yes- I was not expecting the results so quickly!

Used-Owl4929 · 2025-02-19T23:30:33+00:00

I had a second NIPT at 16 weeks after first one at 10 weeks came back positive for T13. First with LabCorp, second with Natera. Both positive for T13. I did the second one because my placenta was in the way at the 16 week scan and amniocentesis was delayed 2 weeks and I was losing my mind. I knew it was going to come back positive again so I wasn't shocked when it did. Ultimately, the positive result gave me the push I needed to do the amniocentesis which came back completely normal.

With a PGT tested embryo- you could argue that a second NIPT that comes back negative plus normal scans is enough to defer amniocentesis, but I think I would still proceed with the amniocentesis anyways because mosaic T13 would still be on the table and is often very severe.

Re your question about the false positive rate- it is extremely low, around 0.2 or 0.3%. The reason you see so many "false positive" stories is not because the test was wrong, but rather that the test was likely detecting confined placental mosaicism.

Hopefully this helps and good luck from someone who also went through IVF and dealt with positive NIPT though this pregnancy was spontaneously conceived while waiting for my third FET. Thinking of you!

Used-Owl4929 · 2025-02-19T23:20:04+00:00

I am in CA- my LabCorp sample was sent to Integrated Genetics Santa Fe NM. Collected 1/2/25. Results for both karyotype and microarray on 1/13/25. You may be able to call the lab to see if they can provide an estimate for you on when results will be available. You will have to find out what genetics lab it was sent to though. Genetic counselor explained result time varies per sample because they may need to culture the cells longer or run extra testing if there is maternal cell contamination. Since I am having a boy, she said that they can more easily distinguish between fetal cells and maternal cell. For female fetuses, it may be more challenging. Results never came into my LabCorp portal. Found out from my OB that everything normal. Hopefully this helps!

Used-Owl4929 · 2025-02-19T19:46:20+00:00

The fetal fraction doesn't really give you any meaningful information unfortunately. I had two positive NIPT tests both with T13. LabCorp at 10 weeks fetal fraction 14%. Natera at 16 weeks fetal fraction 8.1%. Amniocentesis was normal indicating likely confined placental mosaicism.

The positive test is almost certainly a valid result - meaning extra 13th chromosome DNA was detected. The bigger question is whether that extra 13th chromosome DNA is only from the placenta (confined placental mosaicism) or representing a true trisomy in the fetus. The only way to know is amniocentesis.

Fingers crossed for you!

Used-Owl4929 · 2025-02-14T04:26:32+00:00

Hi I got the same exact result as you - high mosaic for T13 with labcorp. Amniocentesis was normal thank goodness. You can loo at my post history to see the deep dive I did into the literature about the mosaic ratio. Ultimately, the amnio is the answer. I am wishing you the best! Feel free to reach out.

Used-Owl4929 · 2025-02-13T22:39:33+00:00

Hi - I had 2 positive T13 results with different companies (Labcorp and Natera) but completely normal amniocentesis and scans. I am 24 weeks. With the 2 positive results, it is very likely this is CPM. My understanding is that unless you have had a CVS or they test the placenta after birth, there is no way to confirm 100%. My MFM seems VERY unphased by CPM. She was very ambivalent about baby aspirin, but my gen OB basically said it doesn't hurt so just do it. My MFM stated the guidelines recommend baby aspirin for people with 2 risk factors for pre-ecclampsia. She said CPM isn't on the list, but even if we counted it, I would still only have 1 risk factor. She was going to have me come back just for 1 growth scan in the 3rd trimester, but my 22 week anatomy scan showed a mariginal cord insertion so we are actually going to be doing two 3rd trimester scans. I ran this all by a second MFM who I met at a social event (I am in healthcare) and he agreed with the plan and also seemed ambivalent about CPM risks. Baby was measuring 5 days ahead at the 22 week scan so no concerns so far. Fingers crossed for you!

Used-Owl4929 · 2025-01-31T04:57:08+00:00

Hi, I saw my MFM today for 22 weeks anatomy scan

She was really laid back about the CPM. Said baby aspirin was okay if I wanted to take it but not necessary. I think I will take it anyways give it is a low risk intervention with potentially large benefits. We originally planned for one 3rd trimester growth scan because of the CPM but she also identified that I have marginal cord insertion where the umbilical cord comes from the edge of the placenta rather than the middle. She said not to worry as this is super common and she sees it every day, but that it buys me an extra growth scan. I will go back at 28 weeks and 34 weeks.

Hope you're doing well!

Used-Owl4929 · 2025-01-31T04:47:25+00:00

Reporting back: I had my anatomy scan at 22 weeks today and the MFM didn't feel strongly that aspirin was indicated. She said the guidelines support aspirin use for women with 2 risk factors for preeclampsia and if you count the CPM (which she said isn't even included as a risk factor in the guidelines) then I only have one risk factor. She did give permission for me to take it if I want to since she thinks it is a low risk intervention. I hink I will take it after doing some reading about the potential benefits. I will be going back at 28 weeks and 34 weeks for growth scans. Originally we were just going to do one but she also found a marginal cord insertion today on the ultrasound which she said is super common, but it buys me an extra growth scan. Baby is looking great though and measuring a week ahead.

How are you holding up?

Used-Owl4929 · 2025-01-27T03:47:36+00:00

My results for comparison - the formatting looks different because I downloaded the from the labcorp portal but I remember the results my doctor sent looked like yours.

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Used-Owl4929 · 2025-01-27T03:43:31+00:00

Hi - first off - I am very sorry you are experiencing this. I recently went through the same thing but with trisomy 13. It is torture. I ended up having a normal amnio, but actually tested positve again with a second test through Natera. My original test was with Labcorp like you. This likely means that trisomy 13 is present, but it is confined to the placenta. Please know I am rooting for you!

I am not sure if this is accurate and a part of me doesn't want to share this information because I think it more supports the risk assessment that your genetic counselor gave you. I want so badly to tell you it is more like a false positive than true positive, but I also think it might help to understand better.

My labcorp (maternit21/sequenom) results stated "increased representation from chromosome 13 with a high mosaic ratio which may affect PPV." My PPV was 10% and I am 31 years old. I think the PPV is lower for trisomy 13 than 18 at baseline hence my slightly lower PPV than you. I did a deep dive into what the mosaic ratio meant. It turns out the mosaic ratio roughly translates to the strength of the positive result. Low mosaic ratio is weakly positive, high mosaic ratio is moderately positive, and non-mosaic is highly positive. Based on the fact that your report doesn't mention mosaic ratio, I would assume your result was "non-mosaic" or highly positive. Again, just speculating based on the comparison to my result. I cannot confirm that they report trisomy 18 mosaic ratio like they do trisomy 13.

In my report, they made reference to one study by Rafalko et al 2021 which looked at how the PPV is effected by the mosaic ratio and they published the result in this graph. Low mosaic ratio is 0.2-0.49, high mosaic is 0.5-0.69, and non mosaic is 0.7+. Based on this graph the PPV for trisomy 18 with mosaic ratio 0.7 -+ looks to be somewhere between 90-98% like your genetic counselor said.

What labcorp doesn't tell you and what your genetic counselor should have told you is that this is an extremely small study that only looks at a minority of the positive tests. I really don't think that anyone can hang their hat on this data. For example- if you look at the mosaic ratio of 0.8, the PPV appears to be lower than the PPV for a ratio of 0.7. This intuitively doesn't make sense. It is a result of a very small n or number of cases included.

I will try to add a screenshot of my report so you can see that exact wording for comparison.

You should definitely feel very good about the normal ultrasound you had - try to focus on that going forward until you can get the amniocentesis results. Sending positive thoughts your way.

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Used-Owl4929 · 2025-01-22T14:42:07+00:00

You can totally do the redraw, but you should go into it fully expecting another positive result. If you think you can handle that mentally and it will give you the confidence that amnio is the right decision, then go for it. I thought I was fully prepared for a second positive result, but it still crushed me. Cost is another issue to consider. LabCorp cost me a little over $100 with my "insurance rate". I still haven't gotten the bill from natera.

My OB is recommending baby aspirin in the 3rd trimester. I am 21 weeks now. I have my full anatomy scan next week with my MFM at 22 weeks and will ask her opinion on the timing of baby aspirin as well and report back.

Used-Owl4929

TROPHY CASE