An interesting question on the Reproductive Partners Fertility Forum about possiblility of doing preimpantation geneic screening for chromosomes (PGS) on frozen blastocysts raises some important points.
Q. I currently have frozen embryo's in La Jolla, we have a 17 month old son and are now starting to discuss a second child. My question is if CGH can be perfomed on frozen 5 day embryos or do they need to be fresh for this procedure? I also understand that it is best if they were frozen via vitrification, but can it still be done if the embryos were not frozen in this manner? Finally is this procedure offered through RPMG?
A. Technically, CGH can be done on trophectoderm biopsies on frozen blastocysts. We have done it.
The problem is that by the time you get results the embryos are beyond the normal time for transfer; not 5 day embryos, but now 7 day embryos and there are no studies I am aware of showing consistent success transferring that late. They could be refrozen, but that would probably seriously impair the embryos.
So this is something that has to be worked out better before I would recommend it for frozen embryos. We will be recommending it in appropriate cases in fresh cycles, then freezing the embryos by vitrification and doing frozen transfers.
Comment: The most recent evidence shows that PGS done on Day 3 embryos using the florescence-in-situ-hybridization (FISH) technique has not been shown to improve live birth rates
in the patients for whom it's been traditionally recommended. Thus the American Society for Reproductive Medicine has deemed it generally not recommended for maternal age, repeated miscarriage or other common indications.
The new technique of biopsying the surrounding cells of a blastocyst and checking all chromosomes, then freezing the embryo by the newer technique of vitrification, and transferring in a frozen embryo cycle should overcome most of the pitfalls of the older technique. Unfortunately there is not enough experience with already frozen blastocysts at this time to recommend it to the person who posed the question,