My name is S. from Boston. I am writing with a question regarding what I am going to be undergoing next week, a second frozen transfer. Just to give you some history, I had a first attempt successful IVF (in vitro fertilization) cycle in 2008 and delivered a healthy baby. We are now trying for baby #2 and had an unsuccessful fresh cycle, and an unsuccessful frozen cycle in the last few months. I still have several frozen embryos so my insurance is mandating that we use them prior to doing another fresh cycle.
I know the success rate is lower with frozen embryos but I wanted to know another opinion, if I should proceed with a fresh cycle if this one is negative. I have 3 frozen embryos left, that are all 6 cell and high implantation potential. I am not optimistic that this one will work, because the other two cycles they put in 2 8 cells and they didn't take. My doctor says there is no difference between 6 and 8 cell embryos, but if that is the case, then why do they always choose to transfer the 8 cells first? I know I could also lose some cells in the thawing process, so does that lower my chances more, and are there are risks associated with the baby, if I do become pregnant this cycle? Thank you so much!
Hello S. from the U.S.,
These are very good questions that you should direct to your doctor. It is his/her responsibility to keep you informed.
Let me take the easy questions first. The reason why we use the 8 cell embryo first is because embryos are graded based on their appearance. Yes, that is we give them a higher grade, the better they look, just like a beauty contest. The cell number is the number of cells the embryo has divided into by that particular day, which I presume to be post-retrieval day#3. Again, we prefer embryos with more cells than less cells. That does not necessarily mean the embryos with more cells are BETTER than the embryos with less cells. In fact, preimplantation genetic testing often shows the opposite. So a higher number of cells does not guarantee a good embryo. The factors that make a good or perfect embryo are not things that we have the technology or knowledge to apply at this point in time. Maybe in the future. My preference is for my embryos to be between 6 cells and 8 cells at this point. Most pregnancies will result from embryos within this range, either grade I or grade II.
Frozen embryo transfers have a lower pregnancy rate probably because the lesser embryos are left to be frozen and the better embryos are transferred fresh. Also, it may be because of the freeze and thawing of the embryos, but the technique has gotten so good that I don't think that is much of a factor any more. But, that does not mean that a frozen embryo can't implant and produce a good pregnancy. I would still recommend that you use them first before another fresh cycle because the medications required are less, AND there are some studies that show that implantation is better if there is no ovarian stimulation, as in Donor cycles. That might be an advantage. You just have to hope that the embryos are still good enough.
I might suggest that you ask your doc to culture the embryos remaining to blastocyst stage. That will be a further validation of the embryos, and may lead to fewer embryos to transfer, but they will be at a stronger stage. That does not necessarily give you a better chance at pregnancy, but the assumption is that if the embryo can survive further culturing then it has a better chance of continuing to implantation. That way, you can further screen the remaining embryos that you have. The ones that don't make it to this point will be discarded, then you will need to move to a fresh cycle. If you have extra blastocysts, you should only transfer two max at this stage, they can be frozen and are in a better stage for the freezing.Finally, there are no added risks for a normal baby if by frozen eggs or embryos. If the embryos are abnormal they usually will not work (implant) or will end in miscarriage. You have not given your age, but this can be a factor in terms of embryo quality, success and genetic risks as well if you are 35 years old or older.
Edward Ramirez, M.D., FACOG
Executive Medical Director
The Fertility and Gynecology Center
Monterey Bay IVF Program
Monterey, California, U.S.A