Sunday, April 06, 2008

All about CGH

I wanted to answer to a couple of your questions on CGH testing, to the best of my ability (which is not great).

I'm not going to pretend that I understand CGH fully. As far as I can tell, it is exactly like PGD, except that they test all the chromosomes instead of just 8 or 9 that PGD routinely tests. However, because of this, the results take longer to come back than PGD. Initially, they were doing the CGH testing on the polar body of the (fertilized?) egg, which is a cell nucleus that is discarded in normal development. This enabled them to get the results in time for a blast transfer, and didn't involve too much damage to the egg/embryo/whatever. However, they weren't picking up all of the problems with the embryos, because they were only looking at the chromosomal make up of the egg, not the embryo, because the polar body does not contain the combined embryo DNA. So they switched, and now, like PGD, they remove a cell from the embryo on day 3, and test that. But because the results take too long to come back to enable a fresh blastocyst transfer to be done, they freeze the embryos and transfer any normal ones at a later day.

It seems about 25-30% of women don't have a normal embryo to transfer. Which is why I signed up for two cycles, so I can have two chances at producing a normal one. If you transfer a normal one, there is a 60% pregnancy rate, and a lower miscarriage rate than with conventional IVF, which is a much higher success rate than with just throwing embryos back in and hoping for the best.

And yes, taking a cell from the embryo can damage it. But most embryos can bounce back and just divide again to replace the missing cells. I've yet to find any information about whether any normal embryos fail to bounce back - I guess there's always the chance. Likewise, the thinking is that normal embryos will survive the freeze/thaw process easily and those that don't survive weren't normal in the first place. However, there is no guarantee on that score. There's always a chance that a normal one could be irrevocably damaged and killed off when it could potentially have become a normal baby.

It is presumably a great option for embryo selection where you have a large number of embryos, as it enables you to select the normal ones for transfer. So it's definitely a good option for PCOS-ers.

So, the question is, why do CGH with only 5 embryos? Why not just transfer all of them?

Well, in the main, because it is free. I am in a CGH study, so all it is really costing me is the flight for the extra trip to Vegas. Or not, if none of the embryos are normal. I will be getting information on the chromosomal make up of my embryos for nothing. I doubt that I would do it if it wasn't for the study, because I am cheap.

Secondly though, where you are a sad sack of a repeat IVF failure, it can be useful to figure out what the eff is going on. I have transferred 17 embryos. Even if I was 43, statistically I should have had a normal one in there somewhere. So why hasn't it worked? Either they are all hopelessly abnormal and I really should hang up my ovaries for good, or I have been transferring normal embryos and there is some sort of implantation problem going on that we haven't discovered yet. This testing will help us get to the bottom of that. I mean, sure, 5 or 6 embryos is not a great sample size. There's a good chance that all these embryos will be abnormal but have it not necessarily mean that all the embryos I've ever produced were abnormal. Hence the two-cycle plan. If we test over 10 embryos, that will give a better idea that my ovaries really are shit. Or, if we find I have one or two normal ones out of 5, and the cycle still doesn't work that gives us a large hint that we really better investigate implantation issues as thoroughly as possible before doing the final cycle.

I hope it will help give me some closure if all are abnormal. It is very hard for me to give up on this whole motherhood dream. And actual proof of the crappiness of my eggs would definitely help me not to keep plowing on hoping for the best.


Aimee & Hannah said...

I really like this study and route you are taking! It makes perfect sense to me and a great plan of attack, esp. if you want to get to the root of the issue. I really have my hopes up high for ya! ;o)

Anonymous said...

That makes a lot of sense to me as well. If all are abnormal (over two cycles), then at least you will know what you are up against. But if not, 60% is a great chance at pregnancy. I really hope the best for you. I even hope to make it to Las Vegas myself in the future. It really does sound like you are getting the best possible care. I can't wait to hear the results. FX

HeidN (Jenny)

Anonymous said...

Ah..gotcha... I was wondering if you were in a study. I hope they find at least one but boy...2 or 3 would sure be nice, huh? Will be keeping you and your little embies in my thoughts!


maybe42 said...

How do you like the clinic in LV? I think it is the same clinic that I might look into. I wish I could be part of a study group - I always seem to be too old (I always ask).

Sarah said...

Thanks for the explaination--I was wondering about the long time between retrieval and transfer. I was just marveling at how I no longer thing about getting a baby, I think about my eggs and finding out if they are 'shit' or or not...