PGS – Preimplantation Genetic Screening

PGS, PGD, CGH – they do all actually mean something different and are used in different cases but essentially they also all refer to the same outcome and that is the genetic testing result of an embryo.

At our previous clinic the method they used was CGH which is an array test. We are not using that method this time.

This time, at our new clinic, we are going for the Next Generation Sequencing which is thought to be slightly more accurate and my clinic refers to it as PGS.

Apparently the CGH method is the preference for when they are working with gene translocations (which we are not) but for everything else it is this Next Generation Sequencing.

Today I had the information session to discuss it all with the scientist and I really did learn some very interesting things – more than I did at the old clinic I think.  I don’t know if this has to do with the fact that I am more widely read on it this time so I had better questions but my understanding now is far greater than what it was before the session, despite having genetic testing carried out on embryos previously.

PGS and error rates

There is a lot of discussion out there about error rates and non viable embryos actually becoming babies and obviously this idea freaks people out. I mean if you are going to test and then an abnormal can be a baby and it ends up being thrown away instead, I mean you’d want to be asking…what the actual fuck?

So here’s what I got from the session today.

  • The error rate is in the region of 2-5%. My clinic quotes 95% accuracy on the all the forms but they believe it to be closer to the 98% mark (how they measure accuracy I don’t know – I wish I’d remembered to ask while I was in there). So if you say 95% that’s 1 in 20 where the outcome will be wrong.
  • Wrong doesn’t always mean that you are discarding an embryo that was read as abnormal when it is actually normal. Wrong can also mean you keep an embryo that is measured as normal when it is actually abnormal. Wrong works both ways and i hadn’t considered that before.
  • If you go check out Braverman’s website (dude who is doing a lot of work with silent endo) it says they try to transfer as many embies as possible (I’m not sure if this means they will transfer those with an abnormal result but that’s what it is implies). If the pregnancy sticks they will go on to do a CVS (invasive test at 11-14 weeks with 1% miscarriage risk) which is more accurate than the PGD testing.  There is a thought by this group that abnormal embryos can autocorrect.
  • I specifically asked my clinic about this scenario. Firstly, in Australia they cannot transfer known abnormal embryos. It’s not a legal thing per se, but more that they would lost their accreditation if they were to do this. Secondly, the scientist seemed to think that the auto correct thing was less likely and that it was more to do with the error rate of the testing. Apparently there are some situations where you will draw a biopsy from one side of the embryo and that will give a normal result, draw it from the other and you will get an abnormal result. That’s just a developmental thing and there’s not anything you can do about it.
  • Because of the error rate my clinic recommends that on positive pregnancy a Harmony test be carried out, obviously the 12 weeks scan + bloods and then if there is any sort of high risk result from either of those then go on to have a CVS (11-14 weeks, 1% miscarriage risk) OR amniocentesis (must be min of 15 weeks I think and 0.5% miscarriage risk). The issue with those laster tests clearly being the miscarriage risk and then also the thought of having to deal with a distressful outcome when you are so far along in the pregnancy. I really hope we don’t have to walk THAT particular road.

So that is all interesting and food for thought. We will still do the testing despite the error rate. And we will certainly do the Harmony test plus the standard 12 week scan for nuchal fold measurement yada yada.

Other interesting info

There were a few more interesting thing pointed out today which I didn’t realise.

  • You can get perfect looking embryos that simply aren’t suitable for biopsy – usually because the inner cell mass (the baby part) is too close to the biopsy point (they do assisted hatching at day 3 and and biopsy through this hole on day 5 or 6). If the mass is too close it means they’d take parts of the baby and they don’t want to do that. It’s meant to be placenta only. If we had one like this then we could transfer without testing but that would be our only option.
  • You can get embryos that don’t make blast by day 5 but haven’t arrested. In this case I can also opt to transfer rather than wait and see.
  • You can do everything right and the embryo just doesn’t cope with the biopsy in which case it dies before you even get a result, or even worse, it dies when thawed for transfer. Imagine if you had one normal result and that fucker died on the thaw. You’d be devastated.

I really felt like there were more options of what might happen when discussing all this with the clinic today – it wasn’t just a “well these are ok to biopsy and we’ll chuck the rest” scenario. I feel like I might have transfer options too. Maybe. At least that the scientist would be looking for those options for me. Like I said before though, perhaps my understanding of the whole thing is just a little different these days. I know more and I’ve been through it so I get it a little better.

I guess we will see what happens when the eggs drop in about a month. Hopefully I make it without debilitating stomach pain. Ha!


24 thoughts on “PGS – Preimplantation Genetic Screening

  1. We did PGS and man am I glad we did. Out of 8 embryos..numbers 1, 3, and 4 were VERY abnormal. They each had over 3 different chromosome issues, which my Dr. said is quite a bit. Scary enough, we would have put #s 1 and 2 in the first round, 3 and 4 the second round, etc. We could have had two miscarriages in a row leading to other issues down the road. The embryos that were abnormal we donated to research and we feel good about that. Not that they were just discarded but that they served a purpose in the end.


    • Yeah I have only ever had abnormal embryos so not doing PGS just wouldn’t be an option for us. We donate our discards to reseach too! I love the idea we could be helping families who go through this have an easier time in years to come because we contributed to the research. 🙂


  2. Wow, I feel like I learned a tonne reading this! I don’t really have any thoughts or advice, but I do find it fascinating how many things could happen with the testing and how many different choices you could be faced with. I guess it’s good for you to know the potentials now so you can think about options in advance.


  3. Is the Harmony test the same as the NIPT- blood test done around 10-12 weeks to look for extra 21, 18, 13, sex chromosomes? Interesting that they strongly recommend that if you do the PGS- people I know here in the US that are doing the PGS/PGD tell me they won’t do the NIPT later on.


    • Hmmmm not surr about names but maybe it is the same test? Yes I would have thought you’d not worry if getting PGS too. I guess the logic is that for these patients there is a cause for concern for whatever reason and because of the error rate they are suggesting you close the gap with more accurate testing. Because I have only ever had abnormal embryos with IVF we would definitely take the extra step to ensure everything was ok. 🙂

      Liked by 1 person

    • It is all a bit bizarre. I know a blogger who did PGS. She went on to have the blood test and came back high risk for a couple of things so had to go for a CVS. All normal on the CVS – in line with PGS result then. Which meant bloods were way out. *sigh*


      • Interesting… well the blood test isn’t working with intact cells or genome, just fragments of DNA that they assign to chromosomes and then compare relative amounts. So even though it’s the most accurate blood test we have it makes sense that the other two- that do use actual cells- would be the same. A little scary to have to go the CVS route though…


  4. Oh my goodness – how do you keep it all in your head? I’d struggle with all of this, and panic and worry and imagine all sorts of things. Luckily you are pretty good at staying relaxed over these big issues, so I think you’ll handle it all with a lot more grace than I would. xxxxx


  5. Pingback: IVF #4 – this ol’ priming is whooping my butt | The Secret Life of Emily Maine

  6. We’re doing the PGS testing as well. We just figure that with our age, we want to make sure we’re using the best possible embies, for the best possible chances. All my lab’s numbers are about the same, as far as stats. I think I’m more nervous about the testing than anything else…I hope they’re not all abnormal! Good luck with yours as well!


  7. Ooo that’s a lot of great info Em. Our new doctor has recommend possibly doing PGD as well for our embryos. He showed me a few really interesting case studies in one case where a lady got 15 blastocysts (15 !!!!! What a dream) but had each tested and only ONE was normal. He then showed me that although these were fabulous looking blasts, they could have transferred 14 before getting to that one that actually worked and wasn’t abnormal. That one blast transfer did end up as a viable pregnancy and healthy birth too which was cool.

    It’s amazing that they can do that and also now I’m feeling as though I probably should have been doing this already because at least then you just know that they are normal! It would rule out so many other factors…

    Thank you for sharing all this info xx


    • No worries. And yes, when you hear about women that do 15 transfers before getting a baby I think it is likely that it is often the scenario this Dr demonstrated. I think in a situation where you aren’t getting many blasts and transfer aren’t working then PGS is a good option if you can afford it. It gives you so many more answers 🙂


      • Sooo many answers! I think I’ve asked this before (sorry!) but I’ve forgotten the answer… Does your clinic charge a blanket price for all embryos or is it per embryo? Our clinic has quoted us $750 per embryo tested and I think it’s to a max of $3000 or something… Is that about right? Xx


  8. All that information made my head reel. I can only imagine, and that not very well, the stress it must play on you. I’m not playing with you when I say this: Don’t forget to yoga breathe and focus on that breath for a few minutes each day!


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