Only showing results from reddit.com
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Reddit
reddit.com › r/pregnant › has anyone ever had a false positive on the down syndrome screening test?
Has anyone ever had a false positive on the down syndrome screening test? : r/pregnant
December 15, 2021 - My younger sister tested positive for Down syndrome until an amniocentesis resulted negative. ... I don't know the details but my husband's mother was told they thought he would have downs and he does not. That was in the 80s so maybe different test ... My god mother had a false positive.
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Reddit
reddit.com › r/babybumps › false positive nipt test stories only please.
r/BabyBumps on Reddit: False Positive NIPT test stories ONLY please.
June 1, 2025 -

I need some hope. I'm 36 years old and had the NIPT test run when I was 10 weeks. I tested 87% positive for my baby having Down's syndrome. At 12 weeks, they looked for soft markers on ultrasound and everything looked normal. Nasal bone was present, back of the neck measured normal. I go back in 2 weeks for a 16 week ultrasound to check for soft markers again. I really don't want to do amniocentesis, and I plan to keep this baby anyway, but I'm really making this post because I need reassurance. I've heard of false positives being a thing, and that my age alone can throw off the test. Please don't post if you don't have a false positive story -- I'm just not ready to come to terms with this yet.

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Reddit
reddit.com › r/nipt › nipt 99/100 t21 hope for false positive
r/NIPT on Reddit: NIPT 99/100 T21 hope for false positive
July 13, 2024 -

I'm beyond devastated. I'm 33 years old from Ontario, Canada, second pregnancy (first miscarriage at 6 weeks). Today I'm 12 weeks. I did the Harmony NIPT on July 2nd and July 11th doctor called saying I'm high risk for down syndrome. Report says greater than 99/100 chance. I have genetic counselling on Monday but doctor already told me I need to do amniocentesis to confirm. Wasn't offered CVS. I have terrible anxiety and the waiting will be excruciating.

I just have no words. I'm losing my strength. I have been trying to get pregnant for a year. I have PCOS and managed to get pregnant with the help of a fertility clinic. In the beginning I was terrified of miscarriage again. Then when I started to feel good I get this bomb.

Is there any hope for a false positive? Perhaps placenta have different DNA than baby? Anyone can share their experience of Amniocentesis? Any stories are welcome.

Thank you!

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Reddit
reddit.com › r/nipt › my false positive nipt experience (down syndrome) – please do diagnostic testing
r/NIPT on Reddit: My False Positive NIPT Experience (Down Syndrome) – Please Do Diagnostic Testing
February 24, 2026 -

I want to share my experience because when I was going through this, I desperately searched Reddit for similar stories.

I was almost 41 when I got pregnant.

At 12 weeks, I did NIPT. It came back positive for Down syndrome (T21).
I was devastated.

At 13 weeks, I did a CVS with both FISH and full karyotype.

  • CVS FISH came back abnormal

  • CVS karyotype came back normal

That was incredibly confusing. My doctor explained that this can happen and recommended an amniocentesis to clarify whether the abnormal cells were confined to the placenta.

At 16 weeks, I did an amniocentesis with:

  • FISH

  • Full karyotype

  • Microarray

All three came back completely normal.

At that point, it was determined that the Down syndrome cells were confined to the placenta (confined placental mosaicism) and that the baby did not have Down syndrome.

For a short time, we felt enormous relief.

Unfortunately, at our 20-week anatomy scan, doctors found serious issues involving the baby’s heart and brain. After several weeks of additional imaging, testing, and consultations, we made the heartbreaking decision to terminate at 23 weeks.

But I want to emphasize something very important:

If your NIPT comes back positive, you absolutely need diagnostic testing before making decisions.

Even though it’s uncommon, false positives do happen. NIPT analyzes placental DNA, not the baby directly. In my case, the abnormal cells were only in the placenta — confirmed by amnio.

NIPT is a screening test, not a diagnosis.

I know how terrifying it is to see that result. I know how hard the waiting is. But please don’t skip diagnostic testing. There are real cases where the baby is chromosomally normal.

If anyone is going through this right now, I’m so sorry. The uncertainty is brutal. You’re not alone.

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Reddit
reddit.com › r/babybumps › fda issues warning about abundance of false positives in prenatal genetic testing
r/BabyBumps on Reddit: FDA issues warning about abundance of false positives in prenatal genetic testing
April 23, 2022 -

They found instances where positive results for certain tests were wrong more than 90% of the time.

And that many of these tests aren’t scientifically sound, causing you to pay—often out of pocket— for cascade of additional partner & parent testing.

“For more rare genetic disorders, caused by small missing snippets of chromosomes known as microdeletions, the agency found that a positive screening result may be a false positive between 70 percent to 98 percent of the time.”

I found this fascinating since my OB asks everyone to take the testing and definitely did not explain this—and neither did any of the literature provided to me by the company we used for testing.

What has everyone else’s experience been?

Article here: https://www.nytimes.com/2022/04/20/upshot/prenatal-genetic-tests-warning.html

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It is important to note that these are not TESTS. They are SCREENS. They are never meant to be used as a final analysis and they require additional TESTING. Many factors can come into play including age, mothers weight, etc. Additionally, as we test more people who aren't high risk then we are going to see more false positives. This number is not being taken in context.
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I found this fascinating since my OB asks everyone to take the testing and definitely did not explain this—and neither did any of the literature provided to me by the company we used for testing. I find it hard to believe that your OB specifically wanted you to be tested for the microdeletions without any known immediate family history of the ones tested for. The norm is only to be tested for T13/T18/T21, triploidy, and sex chromosome abnormalities. These genetic screening are screenings. Not diagnostic tests. They're only supposed to be used for "Hey, we see something funky, you should probably follow up and see if baby actually has this." How many people do the one hour glucose test, fail, but pass the three hour diagnostic? The real problem here is doctors not explaining these tests to their patients, not referring them to genetic counseling before doing these tests, and not having a discussion with a genetic counselor be a required component of receiving the results if anything does look funky. (I also don't think that any medical testing/prescriptions/things like that should be marketed directly to patients, but that's a different struggle)
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Reddit
reddit.com › r › NIPT › comments › ecs533 › false_positive_for_t21_down_syndrome
r/NIPT - False positive for T21 (Down syndrome)
December 20, 2019 -

To all parents in despair, I’d like to share our story of our false positive NIPT.

I was 13 weeks pregnant in March when we received the news (on tuesday) that our NIPT showed positive for T21. Taking in account my age (33) and history, the odds of actually carrying a T21 baby were 75%.

The ob/gyn immediately called me when she received the results and scheduled an appointment for us with a geneticist and MFM specialist the next day (wednesday).

We both had blood drawn and had a talk with the geneticist about our family history. After that the MFM specialist saw us and did a thorough ultrasound which showed a very normal 13 week old fetus. Thus he decided that a CVS wouldn’t give accurate results in case of the T21 being contained to the placenta ( Confined placental mosaicism ) and an amniocentesis was needed for accurate results. We had our luck with a top MFM specialist who is very experienced with early amniocentesis, which most won’t attempt at 13 weeks. It’s a bit painful and scary to see, but with baby in mind it’s for the best. Despite a normal looking baby with 0 T21 markers, he warned us that false positives are rare and to not get our hopes up.

2 days later (on friday) I got the best phonecall I ever had in my life, with the geneticist saying our baby doesn’t have Downs and is a healthy baby boy.

So it was 4 days of agony in total of knowing about the positive, to the relief of discovering our baby is healthy. (I think this is the part where I should mention that I live in a western European country with a very good healthcare system, which is probably why only 4 days went over receiving these results.)

Now, a false positive means either I had a vanishing twin with T21 or confined placental mosaicism. Because the T21 doesn’t just show up in your blood. CPM can result in IUGR, which meant a very thorough anatomy scan at 20 weeks with the same MFM specialist. In our case baby was just fine and didn’t have IUGR.

Now I’m sitting here, very grateful for our (false) positive outcome, with a healthy 4 month old boy.

To those who have just received the horrible news of a positive NIPT, I wish you strength to get through the next few days/weeks and hope for the best outcome for all you!

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Reddit
reddit.com › r/babybumps › maternit21 positive for down syndrome. i’m 20 years old and i’m 13 weeks with my second and am at complete loss and shock. my first baby boy is completely healthy with no health issues. could this be a false positive?
r/BabyBumps on Reddit: MaterniT21 Positive for Down Syndrome. I’m 20 years old and I’m 13 weeks with my second and am at complete loss and shock. My first baby boy is completely healthy with no health issues. Could this be a false positive?
January 14, 2023 -

Has this ever happened to anyone else? Please let me know of your stories. I went in for the MaterniT21 blood test at 12 weeks since I wanted to find out the gender a bit early. However I got the call two days ago saying that I am at high risk for baby to have down syndrome. I’m honestly in shock. I have to go in for a more extensive ultrasound and possibly an amnio or cvs. I’m scared and extremely nervous. No one in my family has down syndrome or health issues. My first baby boy is completely healthy and Im only 20 years old so Im just in shock really. Could it be a false positive? The wait is killing me to find out. I will most likely do the cvs since the amnio would take a bit longer. My mental health is just not doing good right now. I pray and hope that everything goes well for me.

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Reddit
reddit.com › r/babybumps › down syndrome screening result
r/BabyBumps on Reddit: Down syndrome screening result
December 22, 2023 -

So I'm a ftm and im 5 months pregnant. I didn't do the first trimester genetic screening because I didn't want to stress myself out. My midwife team kept mentioning genetic screening, I spoke with husband and he said that we should do it for peace of mind. I caved. I did a test, second trimester screening. My ultrasound showed a while spot in the brain but that said that is common and usually nothing but could indicate down syndrome. The blood test showed that I have a 1 in 55 chance that the baby has down syndrome which is apparently a high chance? So now there is a second blood test that I think is much more accurate, the dna blood test. I will love my daughter no matter what but I am a little more stressed about raising a DS child for many reasons as you can probably imagine. Now im kicking myself for doing any genetic screening at all. Apparently this next blood test still isn't 100% accurate.... even though it claims to be almost that accurate. I don't know if I should bother. Has anyone else been through this BS? Any advice?

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Reddit
reddit.com › r/babybumps › first screening positive for down syndrome
r/BabyBumps on Reddit: First screening positive for Down syndrome
October 13, 2017 -

Got a call from my OB today that my serum integrated screening test came back positive for Down syndrome. She assured me that most of these positive results she's seen have been false positives due to testing too early or something. My doc ordered another screening test and I have my anatomy ultrasound on Tuesday.

Right now to get me through the weekend I just need some positive stories of moms who screened positive but it turned out to be nothing. Please!

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I got the same thing, and we lived to tell the tale. Firstly, one thing that needs to be mentioned -- and I'm a little upset that your doctor phrased it to you this way -- is that the test you did didn't come back "positive" for Downs. It came back with abnormal results which flagged you as higher risk for Downs. The way the first line screening tests work is to identify the people who are at higher risk, so that those people can be monitored to find out whether the baby has Downs or not. So getting an abnormal result isn't necessarily a "positive". It just means that the risk is higher for you than it would be for the average person. It means that they want to do further testing just to make sure. Without knowing exactly what your results were by the numbers, it's hard to say what your situation actually is. For me, it turned out that my risk of a chromosomal abnormality was 1 in 74. Which is a lot higher than the average person -- even the average person my age (I'm 36) -- but does not by any means predict that the baby will have Downs Syndrome. If you think about it, having a 1 in 74 chance of having Downs means that we also had a 73 in 74 chance of NOT having Downs. The next steps after finding out our results were abnormal were to schedule a meeting with a genetic counselor (who is the one who explained the results of the test beyond "abnormal" and made recommendations about what testing to pursue) as well as moving our anatomy scan forward by a few weeks and focusing it more specifically on a closer look at signs that the baby might have a trisomy. After meeting with the genetic counselor, we opted to do NIPT testing, which would be a non-invasive way to test whether the baby has a trisomy or not. NIPT is not a "screening" test, it will say yes or no whether the baby has a chromosomal problem. (It's also the same test people do electively to find out the baby's sex, since it will tell you which sex chromosomes your baby has.) Our anatomy scan revealed no signs of any trisomy including Downs, and the specialist who performed it had absolutely no concerns whatsoever that our baby might have a chromosomal abnormality of any kind. Our NIPT results came back negative for any trisomy. There is, I suppose, a teeeeeeeensy chance that the baby could be born and have Downs. Ultrasounds aren't foolproof. NIPT, like any medical test, can return false results. But at this point, everything that modern technology can tell us shows that the baby probably does not have Downs. I obviously can't reassure you that your situation is just like mine and you are fine and it's all good. But the result you got was not even close to a "positive" for Downs, and does not in any way indicate whether the baby has that or even what the chances are (beyond higher than normal). For me, I spent the days between getting abnormal results and meeting with specialists/having the anatomy scan figuring out what I would do if things escalated further and we were expecting a baby with Downs. It was pretty scary, but I came back with a lot of clarity about how my husband and I would handle a special needs child. I wouldn't necessarily wish it on anyone or want to go through it again, but I did not experience the extreme emotions that I've heard other people theorize when prenatal testing is discussed. I think the best thing to do is to wait and see, and feel your actual feelings about it, rather than looking to others and anticipating that you are supposed to react in some kind of way. I'm not saying it was fun or that I felt perfect composure, but it kind of was what it was. If that makes sense?
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I screened positive! It was a dating error. If your date is off even by a few days and you test at 13 weeks (but really only 12,4) it produces a false positive! Thinking of you!
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Reddit
reddit.com › r/babybumps › genetic screening positive for down syndrome
r/BabyBumps on Reddit: Genetic screening positive for Down Syndrome
June 21, 2022 -

Im now 14 weeks pregnant and I went for my first trimester screening NT screen at 12 weeks pregnant. I just got my results back that my baby has a 1/190 chance of down syndrome. I was in a little bit of shock to hear the news and told my doctor id like to go thru with the amniocentesis procedure to get definate answers which will be done this week. I went back to my doctors office today to get a printed out copy of my results so I could maybe get some more information. My nuchal measurement was 2.0m and ultrasound looked fine but my Papp-a levels look very low at 0.18 MoM and HCG at 1.70 MoM. I see the amniocentesis test has a 1/200 chance of miscarriage rate which scares me and I'm wondering if it's even worth it. My low Papp-a levels are very concerning to me with all the possibilities of bad outcomes with the longer of pregnancy. Has anyone had low PAPP-A levels and had a healthy pregnancy? I'm freaking out and having anxiety. Sorry for the rant.

Find elsewhere
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Reddit
reddit.com › r/babybumps › if you were tested for down syndrome (both at embryo stage and with the nipt) and both came up negative, is there still a chance the baby could be born with down syndrome?
r/BabyBumps on Reddit: If you were tested for down syndrome (Both at embryo stage AND with the NIPT) and both came up negative, is there still a chance the baby could be born with down syndrome?
February 3, 2022 -

We might have been the recipients of some misinformation but my question is so specific that it's hard to find the answer. We did IVF so our embryo went through genetic testing but we also did the NIPT testing offered at a later stage through the OBGYN. Both came back clear! However, our maternal ages are 40 and over so we're a bit worried and a friend told us that we're not out of the clear yet. Is there anyone out there familiar with the science who could maybe put our mind at ease with some stats or studies? Thank you in advance!!

EDIT: to clarify i did have the anatomy scan already and there were no concerns. Just a slight soft marker of parenesis (Spelling?) which apparently is so common it's not a great soft marker.

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Reddit
reddit.com › r/nipt › genetic testing came back positive for down syndrome. struggling with processing. thoughts on amniocentesis?
r/NIPT on Reddit: Genetic testing came back positive for Down syndrome. Struggling with processing. Thoughts on amniocentesis?
December 11, 2025 -

I had genetic testing done at 12 weeks due to my age (37) and honestly just for peace of mind. Results came back a week later positive for T21. Based on my age, the age adjusted PPV is listed as 97.5%. We were shocked and have been trying to process. My ob sent a referral to an MFM Dr for a consultation who can’t see me for a month. At the appointment, the dr will do an ultrasound and likely recommend further testing to confirm (an amniocentesis as I will be 17 weeks at this point). We are trying to accept things rather than hope for a false positive. Feeling extremely overwhelmed and scared and just praying for the baby to be as healthy as possible. Has anyone chosen not to do an amniocentesis due to the possible miscarriage risk? From what I can see online, NIPT results are 99% accurate nowadays. My husband and I are torn on doing the amnio because we won’t be terminating the pregnancy either way but think we might feel some comfort having a 100% confirmation from the amnio, although 99% accuracy feels basically like a 100% confirmation (regardless of being a screening and not diagnostic). Not sure if the confirmation outweighs the possible risks and just curious about other people’s experiences. I’m a first time mom feeling very lost and scared. Any help and advice is much appreciated!!

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Reddit
reddit.com › r/pregnant › increased chance of down syndrome after screening tests.
r/pregnant on Reddit: Increased chance of down syndrome after screening tests.
November 13, 2022 -

(I posted this in r/babybumps as well but wouldn't let me share the post across so I have pasted it!)

Hey all. Currently growing baby #2 and we've just had our "12 week" scan.

Nothing was mentioned at our scan and everything with baby seemed to be perfect (to me, anyway) but with the NT measurement taken and my bloods, the screening test results came back as "increased chance" of baby having down syndrome.

We were advised it's a 1 in 42 chance, which I've been advised is 2 point something % chance.

Wasn't overly keen on having an amnio or CVS, so I opted for NIPT - which I had done yesterday and just waiting on the results. (Could take a week/just over😔)

I've read a few posts on here regarding this and I'm also aware of r/NIPT... but I don't know if it's helping me or making me feel worse. I take everything with a pinch of salt anyway as I know everyone's circumstances are different.

They never told me if it was because of the NT measurement or if anything was amiss on the scan, they also never said it was down to my blood results, they just mentioned it was a combination of both, and including my age when baby is born (which would be 31)

My gut is telling me everything will be fine, trying to ride on that 97(ish)% chance that baby doesn't have down syndrome, and it's not about that so much, I just worry that there may be other defects.

I think I just feel a bit scared, and in limbo whilst we are waiting for the results.

Thanks all for reading.

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The NIPT is more sensitive as a screening tool. It will give you a better idea, but is not diagnostic. I would personally skip to the the amnio, which is diagnostic. But since you’re having the NIPT, if it’s negative, that’s great and you can probably rest easy. I would do the amnio because I would abort if my baby was trisomy 21. If you wouldn’t abort, no matter the results… Maybe the risk of the amnio isn’t worth it to you. But, maybe doing amnio to verify a diagnosis, and rule out other genetic conditions would be of value to you and your care team- it can help them prep and plan for NICU treatments, surgeries etc that might be needed. With amnio there is a small risk of miscarriage. (Less than 1/100), but please be aware that the all-around risk of miscarriage or stillborn is about 1/175 in the USA. So when it comes down to it, not a huge risk by comparison. Just consider what you’d do with the diagnosis and that can guide your decisions on diagnostics.
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Hi there, I just went through something similar with my second. I was flagged after nt test/blood work as having 1:110 chance (for my age should have been 1:200). Do you have a copy of your test results? Mine was from the blood work alone (nt measurement was fine). I did the nipt. It took about two weeks to get back where I live, and everything came back normal so I didn’t do any further testing with amino etc. the waiting sucks, but doing a lot of reading it sounds like this happens quite often. If you have any questions, let me know.
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Reddit
reddit.com › r/babybumps › chances of a false negative on nipt
r/BabyBumps on Reddit: Chances of a false negative on NIPT
January 23, 2022 -

Had the NIPT test at 12 weeks came back negative. Had my 20 week scan everything was normal, baby has slightly shorter femurs, had a private 4d scan at 27 weeks all normal. Last week went for growth scan at 37 weeks and he's got a dilated kidney. Google says this is a soft marker for downs syndrome. Freaking out a bit...Feel like I should of got an amino to be sure now

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Just wanted to jump in and say that the r/NIPT subreddit is an AMAZING place. I had an NIPT with a positive (it was a true positive) but I learned a lot and had a lot of support in that forum for everything that came next. If your NIPT is negative or « low risk »- your odds of Down’s is very VERY low. These tests are considered gold standard because they err on the side of false positive- they want to make sure they catch EVERY true positive and sometimes then identify those that are not truly positive, but the chance of missing something like Down’s syndrome is 1 in 10,000 or more. It’s extremely accurate. Measurements of a soft marker are just that- completely non-specific and in the setting of a negative NIPT, nothing to worry about. Your doctor can talk to you more about a dilated kidney but if they aren’t worried, you shouldn’t be either. It’s important to remember that there are plenty of very rare diseases that NIPT doesn’t screen for— if that was the only thing they saw that was slightly abnormal, I don’t think there’s too much cause for concern. If your doctor was worried they would have you do an amnio or follow up with a high risk Maternal-Fetal-Medicine doctor for further screenings or tests. Soft markers are useful when there are multiple showing up- but in the setting of NIPT they are rather useless (unless they are signaling for another disease not tested for on NIPT). An Amnio is not a risk-free procedure. If there’s a real reason to be concerned (and your doctor or a genetic counselor) is encouraging you to get one, of course, get one. I had one done because my NIPT showed I was very high risk- and it turned out to be OK. One soft marker with a negative NIPT? Talk with your doctor about your concerns, but that wouldn’t be enough for me to get an amnio unless there were other reasons. Please be reassured by your NIPT results, they are incredibly sensitive and specific. There is a 1 in 10,000 chance that NIPT is wrong, there is a 8:9 chance that the soft marker is wrong (and probably way more than that in the setting of negative NIPT).
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Not a doctor or an US technician but I’d say the chances that Down syndrome was missed in a NIPT test, and 2 ultrasounds is pretty unlikely.. there are other causes of kidney dilation, I’m sure your doc will go over the potential issues/solutions with you
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Reddit
reddit.com › r/pregnant › false negative on genetic testing for down's syndrome??
r/pregnant on Reddit: False negative on genetic testing for Down's syndrome??
March 21, 2023 -

Does anyone know of any mothers who have given birth to a baby with Down's syndrome (or another genetic disorder), despite being "low risk" on all genetic screenings?
(Note- title is incorrect in calling this "false positive", I've edited this text to clarify, but could not edit the title.) I (39f) am 30w 4d. Baby was measuring on track through 28w, when she dropped to 9th percentile. I had an appt with high risk Dr yesterday and they confirmed she's actually measuring at 3% (symmetrical FGR). Dr said everything looked perfectly healthy on the ultrasound, and prior to this, everything has been on the right track (all genetic testing was low risk, 20 week scan showed no abnormalities, amniotic fluid and placenta etc has all been normal.) dr shared that there's no markers for Down syndrome, genetic disorders, skeletal dysplasia, congenital heart defects or anything else - but we will be monitoring 2x a week (once with OB, once with high risk Dr) moving forward with plans to deliver at 37 weeks if things stay the same (earlier if they worsen). High risk dr also explained that while all genetic tests showed low risk, and she sees no indication of anything abnormal anywhere to suggest otherwise. (other than small size), no test is 100% guaranteed (outside of amniocentesis, which I prefer to avoid). ----Dr said the reason for baby's small size is "unknown," and it could be 100% healthy and normal, but just "constitutionally small" (my son (4m) was determined to be "constitutionally small," when he started measuring behind at 35 weeks... we did NST 2x/wk but did NOT need to return to high risk Dr, and he caught up in size by the time he was delivered, healthy and on his own, by 38w 6d, at 6 lbs 2oz). My fiancé is 5'10 and was born at <6 lbs; I have always been very petite; prepregancy 5'3, 90 lbs; born at 6 lbs). I am terrified that there is something wrong with my baby, despite all the low risk testing.--We don't have any known genetic diseases on either side of the family, but I keep reading about symmetrical FGR and how it's less common (30% of FGR cases) and typically linked to genetic/chromosomal problems and identified before 32 weeks). When explaining all the risks, the doctor noted that with even with the "low risk chance of 1 in 10,000" for Down syndrome on Panorma, there still is that "one" person out of the 10,000... I know she probably has to say that to everyone, but now that's all I can think about---- so scared I've been going through this pregnancy thinking we have a healthy baby who passed all the screenings, just to find out she's the she's the 1/10,000 born with Down syndrome or another disabling genetic condition not picked up on the screening.... .

TLTR: Baby suddenly measuring small (3rd percentile) at 30 weeks (everything else healthy/normal, genetic screenings all low risk, no known cause for small size) Could it be Down's syndrome/another genetic disorder, despite being "low risk" in all the genetic testing? Is anyone aware of any mothers who screened as "low risk," but ended up being that 1 out of 10,000? Thank you so much for taking the time to read this, and for any insight you can share.

EDIT: clarifying that this is about "low risk" on genetic testing (and not about getting "false positive as title incorrectly stated.) I apologize for any confusion-- thank you!

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Reddit
reddit.com › r/nipt › 2nd trimester- maternal serum screening positive for down syndrome
r/NIPT on Reddit: 2nd Trimester- Maternal Serum Screening positive for Down syndrome
June 14, 2022 -

I am extremely distressed to find out that my 2nd trimester screening is positive for Down syndrome (1:90). I am waiting for my NIPT results now. Right now it’s my 19th week. I just want to know if such screenings have false positives? I am really depressed I seriously don’t know what to do. I am only 29 years old.

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Reddit
reddit.com › r/nipt › labcorp maternit21 t21 down syndrome low mosaicism false positive story
r/NIPT on Reddit: Labcorp MaterniT21 T21 Down Syndrome Low Mosaicism False Positive Story
July 30, 2025 -

I lurked on this sub for a few weeks when I first got my NIPT results, and created a burner to share my story. My primary motivation is that it can be a helpful resource for other people who have gotten the same result as mine i.e. MaterniT21 'low mosaicism' results as there are so few cases like this.

I'm 34F FTM, we were just thinking that this is the 'right time' to get pregnant and before we even started trying and, boom, I was pregnant before I could even figure out the ovulation strips. It was all a bit of a roller coaster with early prenatal OB visits, all looking good with no risk factors identified.

May 23

We did our first 11.5 week NT scan and it was 1.3mm, which is as normal as it can be right at the middle of the bell curve.

June 1

When they did my NIPT, I wasn't even thinking much about it other than it will let us know the baby gender ASAP. But then a week later everything changed.

I truly love my OB and she is one of the smartest and compassionate doctors I have met (and I come from a family of doctors so that's saying something). I woke up early June, to a series of missed calls from her and voicemails asking to callback to talk about the NIPT results.

When we called her back, she said that the test came back with abnormal results - it says that I was flagged for T21 Down Syndrome Low Mosaicism. She said this low mosaicism result isn't as sure as the regular full on or high mosaicism result, and given my normal NT, while she can't say its nothing, she feels cautiously optimistic this could be a false positive. She specifically said, she recommends doing an amnio as CVS might also have false positive due to possible CPM which is more likely with this 'low mosaicism' result.

The exact results:

This specimen showed an increased representation of chromosome 21, suggestive of low mosaic trisomy 21, which may affect the reported PPV (Rafalko et al, 2020). In placental testing, trisomy 21 is a common finding that is often confined to the placenta (CPM), Grafi et al, 2014. However, true fetal involvement is associated with phenotypic abnormality. Genetic counseling, confirmatory diagnostic testing, and clinical correlation are recommended.

Fetal Fraction: 18%

She referred us to the mandatory Genetic Counselor visit in 1 week and helped schedule the amnio, which would be in 4 weeks.

To say this was a shock to us would be an understatement. I panicked and cried and cried some more. But then I did some research to learn more about NIPT, genetic testing and how chromosomal abnormalities work.

WHAT I LEARNED:

Disclaimer - I am not in the medical field, but I do have experience reading scientific papers from my research lab days in college. Mods, please correct if any of the info is incorrect - I'm also happy to make edits if you flag it.

  1. How chromosomal abnormalities happen: Chromsomal abnormalities can happen in two stages. First is mitosis, i.e. when the cells are first dividing after fertilization and meiosis, i.e. when the egg divides before meeting the sperm. The former is more common in younger women and is usually corrected, and the latter is more likely in older women and usually persists. Me at 34, probably could fall into either group, but possibly more likely in the latter.

  2. NIPT tests for something called cell-free DNA which are fragments of fetal DNA floating around in the mom's blood, which is potentially shed from the very outer layer of the placenta (called the cytotrophoblast). This is important because as you go in more inner layers of the placenta they are likely to get corrected, more so in younger women. On the flip side for rare cases the abnormality can only happen in the inner layer, so NIPT would be a false negative.

  3. This is why if you get a positive for NIPT, doing a amnio should always be the right choice because that is the only test that actually looks at fetal cells - a CVS can only tell you what's happening on placenta, so if you had a false positive because of CPM, it will just repeat the same result.

  4. NIPT saying they have a 99% accuracy of whatever, doesn't mean that all positive results are 99% accurate. It means that both for positives and negatives, overall they are 99% accurate - and given that vast majority of results are negative, the rate is mostly representative of that. In reality for positives, the PPV can be as low as 20% for some triosomies and age groups.

  5. When a fetus is positive for a triosomy, it can be full trisomy i.e. all cells of the fetus have 3 of certain chromosome, or mosaic i.e. only a portion of the cells have 3 of a certain chromosome. Mosaic babies can be symptomatic or not depending on the ratio of mosaicism and where its expressed.

  6. In general mosaic T21 is much less common than full T21. Additionally, T21 cpm is also less common than full T21 - CPM overall occurs in ~1–2% of pregnancies screened by CVS, but only 3% of CPMs are T21.

  7. Now for the kicker, this NIPT so called 'Low Mosacism' has absolutely nothing to do with true mosaisicm. Mosaicism ratio for them just means that if they thought there were 100 fetal cells, not all 100 were flagged to have triosomy. If its over 50 and under 70 then its high mosaicism, if its under 50 and over 20 its low mosaicism. See here for more details, but to simplify it essentially means that whatever statistical model and imaging software they used found partial signal - that's it. It could mean mosaicism, it can mean full triosomy, it can mean nothing.

  8. LabCorp's 'Mosacism' gimmick (I feel like I'm being snarky but honestly I wish they picked some other term because its astoundingly stupid misnomer) only started being reported fairly recently but they did a retroactive study on their results from around 2019, for about a couple of years of data iirc. You can see it here. Note this data is biased because it was from a time when NIPT was only done for high risk women for the most part, and this is their own lab data. However, here you can see only for T21, only 1 in 10000 cases get a 'low mosaicism' result, and from the 7 cases where they had a follow up with this result the PPV is 28% i.e. 2 people turned out to have t21 either via CVS or Amnio. Now if its CVS it could be CPM but they don't specify that. You can have your own interpretation of these results, but to me 7 cases is noise. It's statistically meaningless. And given it could be been CPM confirmed via CVS its even more trash in terms of data. For them to report a PPV based on this is a joke, to call this its own category of 'low mosaicism' results is even more alarming. I think they would be better off flagging it as just 'atypical' t21 like other companies and call it a day, but no they had to come up with this bs. Anyway, rant over (for now).

  9. Given how flimsy this data is, I looked high and low for other people with this result and that's how I ended up on this sub. I found two examples - one was a 43F case where the NIPT was done after 17 weeks (NIPT gets progressively less accurate after week 12 - see here) and another one was an IVF case where the embryo was chromosomally normal, mothers age unknown. Both cases as you can see turned out to be true positives. But again, it supported my hypothesis that this 'low mosaicism' is just a atypical result that can happen for any number of reasons and whether it will actually be a true positive or false positive is a coin toss almost. The only factors working in my favor where the normal NT and normal ultrasound.

  10. About 50% of T21 cases show a soft markers, even though a lot of the historical soft markers are completely meaningless now unless at an extreme point like 1st percentile or something e.g. femur length to head ratios etc. Regardless a lack of markers doesn't really really help the case that its a false positive, but the flip side a presence of markers can detract from the case.

  11. So, given these results we have a few things that could have happened (a) this is just normal t21 and for some reason the test couldn't detect it right but that is odd given high FF, (b) its mosaic t21 so that's why so few cells were flagged (c) its CPM that is only a few placental cells have t21 or (d) its statistical/algorithmical noise of the test given how rare the result is. If you asked me at that point which one I would say its a total toss up, but my doctor was a believer of (c) or (d), because while unlikely for most people, with my rare results they are more likely.

  12. As I mentioned before amniocentesis is the only test that can give us the real answer of what's going on with the fetus. Its done in three steps.

  13. The first is FISH where they basically put n random fetal amniotic cells under fluorescent light with a probe that detects certain area of each chromosome for 13, 18, 21, X and Y. That way they can get a quick count of any cells that have more than the normal number of any of them. While it's very good for confirming or ruling out the common trisomies, it can fail if for some very rare reason the area that is used for probe is somehow microdeleted.

  14. The next is karyotype where they actually culture the cells and look at the full 23 chromosome pairs in full detail unto 10 MB resolution. This will detect any missing or extra chromosomes outside of the common ones and also if any chromosome is missing or duplicated partially upto above 10 MB of data (the whole 46 is about 1.5 GB of data). Data shows that karyotype catches about 0.7% of cases missed by fish for common trisomies - see here.

  15. The last test is the microarray that looks at deletions and duplications under 10 MB of data. They produce new genetic clinically significant abnormalities that are missed by FISH and Karyotype for 1.6% of cases, see here, but that probability is possibly higher with with ultrasound markers. Microarray is not really related to triosomies per se but they can be clue sometimes for atypical and discordant NIPT results. Note, this test can also often flag some small variants called variants of uncertain significance that are different from general population but we don't know if they cause any clinically significant symptoms. Some parents don't want to know about these as it needlessly causes worry.

June 7

We met our genetic counselor, who tells us again that this 'low mosaicism' result could potentially be CPM and she thinks our odds are 70% of being false positive. She repeats that a CVS would be pointless and by this time we have done our research so we agree fully.

She points us to a study that shows that for cases of placental T21 mosaicism (not full placental T21), 30% of the cases had true fetal T21 or T21 mosaicism. (link). At this point though, because we know the NIPT result has no way to tell if anything is mosaic or not, this could be meaningless for us.

She orders an extended FISH with 200 cells to make sure to catch any mosaicism just in case, along with karyotype and microarray.

July 1

After one of the most challenging and harrowing periods of my life with this tortuous wait, where we can't feel one way or another, we finally have our amnio. Needless to say the time was painful, and the only happiness and sanity I had was while being at work distracted completely. But of course you can never truly forget as your body reminds you of your growing baby through all the signs and symptoms of pregnancy. I think I cried more during this period more than any other in my life, feeling at the same time frustrated but also ungrateful for feeling so, because we got a higher chance at a false positive than most. And even beyond that, I'm healthy, my husband and our family and pets are healthy, we can have another baby - how can I allow myself to be so upset? At the same time, it might not be this baby, who I'm already attached to and the thought of letting him go breaks my heart. This limbo period is truly a nightmare that I don't wish on anyone.

The amnio itself, the whole process goes super smooth, the MFM in charge walks us through each step and she tells us baby in ultrasound is perfectly normal with no soft markers whatsoever.

July 2

We get back our FISH result, with 100% normal cells from the 200 tested detected. I literally fall to my knees in tears, so so grateful beyond belief. Our GC tells us at this point, she would be 97% certain it was a false positive.

But me being me, of course I can't be fully easy in my heart.

July 14

We get back our karyotype, also completely normal. At this point our odds are at above 98% of a false positive for any genetic abnormality. Almost impossible we have a Down Syndrome case, mosaic or not.

July 23

We do the detailed anatomy scan, with extra care taken because of the NIPT flag. A month ago I didn't know I would reach this milestone, see my baby to summersaults, see his face shape forming, his little feet. The results are once again completely normal after an hour of getting every angle of his hands (we waited 10 mins for him to fist and unfist his palms), heart, brain, kidney. Baby is growing big and healthy and very active to boot.

At this point our odds of any genetic abnormality, even micro duplications or micro deletions is low. If anything is abnormal at this point it would be unrelated to the original NIPT or my age - it's something called 'de novo' mutations that happen completely randomly to anyone i.e. its general population risk.

July 29

After two long months, we finally get the last piece of the puzzle. Microarray comes back completely normal, not even a benign variant or variant of uncertain significance. Doctor thinks while we can keep an eye for signs of CPM, she's not worried particularly.

We still don't know what the future holds, there's still maybe 1 in 10000 chance that there is some hidden problem the amnio didn't catch but regardless, I think I can now finally allow myself to be happy, feel joy in the little kicks I can sense in the quiet moments of nighttime, call my baby by his name, and truly feel hope that I can meet him soon.

MY THOUGHTS ON NIPT AND PRENATAL GENETIC TESTING:

Now that I'm on the other side this genetic testing experience (of course we can still only hope that rest of the pregnancy will be smooth and we will have a healthy baby), I found myself reflecting on a few thoughts. These are completely my subjective beliefs for the most part so do with that what you will.

  1. Timing and targeting: NIPT can be a great tool to give parents some early reassurance and also a sneak peek at baby's gender. While I understand that it's done at 12 weeks because of accuracy reasons, for the vast majority of women who are in the low risk group, is that really worth it? For me it was not, specially given I would have opted for an amnio regardless. This two months I spent, planning TFMR, crying, negotiating, stressing - who did this benefit? I found myself almost being jealous of my mom who went though her pregnancy in blissful ignorance with just regular ultrasounds to make sure the baby is growing well. With all these new tests, what benefit and what harm did I do to my baby? More than 3M women give birth every year, even 1% of them with false positive results is 30,000 women. T21 false positives are fairly low, but but T13 and T18 where false positives are more rampant - is it really right to subject every woman blanket to this situation? If I were to be pregnant again, I would opt out of NIPT and go straight to Amnio, knowing what I know now.

  2. Labcorp's testing and reporting: I've already ranted in detail about the 'low mosaicism' misnomer so I won't repeat it again. But something that my GC said alarmed me - she mentioned she saw another couple of these 'low mosaicism' cases last month. Given how rare the result is by Labcorp's own data, what are the chances of that happening? Take this with a ginormous grain of salt, and the disclaimer that I go to one of the biggest and best hospitals in US in the biggest city so they probably handle more abnormal cases than usual, but still to me it's fishy. Did labcorp change something in their algorithm? did something go off because the testing population is changing so rapidly i.e. everyone as opposed to high risk?

  3. NIPT is not diagnostic: I know it's repeated over and over in this sub, but it's so so important we digest this. Don't make decisions based on NIPT, as it can never be the source of truth for your baby. CVS cannot be the source of truth for your baby. Amnio is the only test that can be that. I was lucky to have a very good medical team, guiding us each step of the way but I know that is not the reality for a lot of women. Science is a blessing but it can sometimes also be a curse when we believe in false precision and make irreversible decisions based on that.

This was a long long post, and if you read the whole thing hopefully it provided some insights and data points that can be helpful for you. Happy to answer any q's but given this is a burner I might not come back to this account often. Wishing you the best of luck for your journeys, and wherever you land I hope you find peace and happiness.

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Reddit
reddit.com › r/babybumps › positive quad marker screen for ds
Positive Quad Marker Screen for DS : r/BabyBumps
July 7, 2021 - It does not mean that 5% of positives are false and 95% are true. It means that of everyone who does NOT have a fetus with Down syndrome, 5% of those people will have a positive quad screen. So if they tested 100,000 women who all did not have a fetus with Down syndrome, 5,000 women would have ...
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Reddit
reddit.com › r/babybumps › tested positive for high risk of down syndrome. anxiously waiting for nipt results..
r/BabyBumps on Reddit: Tested positive for high risk of Down Syndrome. Anxiously waiting for NIPT results..
May 12, 2020 -

Happy update: NIPT came back! Low risk, cleared of all genetic conditions they tested for!

Hi Everyone. I'm 12 weeks in.

NT was 3.1mm and after the blood screening results the nurse called me back saying I'm positive which means I have a high chance of having a down syndrome baby. She said I have 1 out of 95 chance which is considered high. My hubby and I rushed to get the NIPT test done and we're waiting this week for the results. I don't know how I'm supposed to function this week. I only told this news to my sister because there's no point in having our parents worry with us this week. But this has left me feeling like everyone is out of context. They're talking about baby showers and I'm in a completely different mindset. Keep me company?