Dear Mamta, first, Merogenomics is not qualified to answer this as we focus on DNA testing part. However, by association we have small familiarity with other pregnancy tests. If we understand correctly, positive result would indicate there is increased possibility the baby might be affected by imbalance in chromosomes, however, this is not going to be absolutely certain either! As you might have seen from the video, these blood tests can often result in false results and therefore will require confirmation. Very likely you will have an appointment booked with a genetic counselor (or other qualified healthcare professional) to help explain the results and the risk estimate of how baby might be affected. You should be informed, if we understand the process correctly, of test options available to you to confirm the result (IT ALWAYS HAS TO BE CONFIRMED) and that will include invasive options, but can also include NIPT.

If it is negative result it means the test did not discover any chromosomal abnormalities. This is not testing directly in the baby, but placenta. But since placenta and baby come from same fertilized egg, the assumption is that negative result suggests the baby is fine. That might not always be the case but usually negative results are highly accurate results.

Merogenomics n

Dear Aysegul, thank you for your willingness to share your story. First, I'll mention that I am not qualified to offer any recommendation and will simply share my notes with you that I collect from past studies of published scientific literature (I provide references for you). Second, this is complicated answer! Let's discuss CVS. Whether CVS can be diagnostic towards info related to the status of the fetus depends on what type of cells were studied in the process and which type of trisomy is investigated. There can be cells studied from short-term cultured villi (STC-villi) or from long-term cultured villi (LTC-villi). The origin of the cells that are investigated are different in both techniques: cells in STC-villi are derived from the cytotrophoblast, the outer cell layer of CV, and these are also the cells that provide the DNA that is investigated by NIPT. More importantly though, cells of LTC-villi are predominantly from the inner cell layer, the mesenchymal core, and these cells derive from progenitor cells that lead to both the placenta and the fetus, so this cell line is more representative of the fetus state. Thus the gold standard for cytogenetic analysis of CV is investigation of both STC- and LTC-villi. So you could inquire which cells were investigated. If LTC-villi cells were investigated, mosaicism can still occur (where fetus is fine) but this is more rare than mosaicism discovered in the STC-villi. Plus trisomy 21 in STC-villi alone is already assumed to be a status of certain abnormality (Reference: journals.plos.org/plosone/article?id=10.1371/journal.pone.0146794 - I could not confirm as to why that is). Now as for amniocentesis. This is going to be the most accurate method available to you and my understanding is would be the next test after high risk test result instead of CVS (Reference: s3.amazonaws.com/cdn.smfm.org/publications/223/download-f5260f3bc6686c15e4780f8100c74448.pdf but there might be more updated version of this now). CVS can be done earlier though. The reason why amniocentesis is not typically offered prior to 15th week is because of increased risk of pregnancy loss and resulting birth defects. If your CVS did suggest mosaicism (only portion of cells showing trisomy), then indeed amnio would be the next way to go (Reference: www.nursingoutlook.org/article/S0029-6554(14)00002-5/fulltext). But if CVS result already did not indicate mosaicism itself (where some investigated cells are normal and some are not), it appears that current approach does not recommend relapse to amnio testing (Reference: www.nature.com/articles/gim201791.pdf?origin=ppub). However, that same publication does state that on rare occasions discordant CVS and amnio results have been observed (CVS positive whereas amnio is negative and I checked one of the references which listed one such reported case). So if you want to be 100% sure, than indeed there appears a very small possibility that placenta is trisomic whereas fetus is not but that would be very rare it seems. Thus I am not sure if that makes you eligible for further amnio testing. Everything I researched in published info indicates this result would be considered accurate already. I hope this helps with some background info and I wish you all the best!

@@Merogenomics this was very helpful. Thank you so much for taking the time to write me a detailed answer.

@@aysegulkarzek7400 how did your pregnancy ed up? I am going through the same thing

Hi unfortunately I terminated the pregnancy. After that I had the fetus tested for trisomy 21 to eliminate the possibility of any mosaicism and the fetus had trisomy 21. But after almost 2 years I am still hurting about this. I regret not having the baby. I hope you make the right decision.

Hi unfortunately I terminated the pregnancy. After that I had the fetus tested for trisomy 21 to eliminate the possibility of any mosaicism and the fetus had trisomy 21. But after almost 2 years I am still hurting about this. I regret not having the baby. I hope you make the right decision.

Dear Samantha, I am truly sorry to hear about your experience. First, please confirm below information with your genetic counselor to ensure you get the most accurate information. The situation you describe appears to be quite rare and understudied. It is precisely because of false negative NIPT results that it is being investigated to a greater degree. I was able to only find one good publication on the topic (journals.plos.org/plosone/article?id=10.1371/journal.pone.0146794). The term you are looking for is either i) generalised mosaicism confined direct normality (GMDD) - this is where the fetus is affected as well as the mesenchymal core of the placenta, but the cytotrophoblast of the placenta which is where the DNA targeted by NIPT is from, is normal (these are different cell types that make up the placenta); OR ii) confined fetal mosaicism (CFM) where placenta is completely normal whereas the fetus is affected. However CFM is expected to be extremely rare, authors estimate only 0.003% of the time. In the case of GMDD, which can be due to either cytotrophoblast of the placenta being normal or mosaic at a fraction that is too low to be detected by NIPT, authors estimate to be 0.2% of the time for trisomy 13, 18 and 21, but trisomy 18 is especially more prone to this event. Because of the rarity of these events, authors encourage that cytogenetic studies be undertaken on both the fetal tissue and the placenta precisely because of how medically understudied this is. I hope this helps.

How is your baby now