To Vitrify or Not To Vitrify-- That Is the Question...

I watched this video earlier this week, and I’m still reeling from it.  It was released in 2009 by RMA, the reproductive clinic I'm working with, and it describes the egg freezing process.  What horrified me is that the video says that my clinic uses the “slow freezing method”.  All this time, I thought they used vitrification, which is the latest egg freezing technique much ballyhooed as the new breakthrough in successful oocyte cryopreservation.

One of the reasons I’m inspired to do undergo oocyte cryopreservation now is because of the advances made in egg freezing techniques, namely vitrification.  I felt cheated and outraged that my clinic might have misled me about the technique they use.  So many articles they’re associated with tout the benefits of vitrification.  Even their website touts vitrification as a superior technique, which I think is extremely misleading if they do not utilize it themselves!  In a recent NPR story regarding egg freezing, one of the doctors are my fertility clinic, Dr. Alan Copperman, discusses the promise of vitrification (see under "Technological Innovations").

I’m positive that I asked the question about the use of vitrification in my consultation and that I got an affirmative answer.  This video is over two years old, and vitrification is a relatively new freezing method, so I'm hoping the video is outdated.  I’ve sent an e-mail to my IVF coordinator to confirm. 

By way of comparison, NYU Fertility Center uses both vitrification and slow freezing because there isn’t enough evidence that one is more proven than the other (this is based on a published interview with Dr. Jamie Grifo that I can't find anymore).  I did call NYU for a second opinion back when I was first exploring the procedure-- but they never called back.  Some other fertility clinics, such as the Pacific Fertility Center in the Bay Area, use vitrification only.  Cornell does not support egg freezing at all.

But even if they don't use vitrification, I feel "pregnant" with working with RMA in part because I am so far along (I've done all the necessary tests, training, etc., and I can begin my treatment cycle any day now), plus the fact that NYU, the only other clinic I'd work with in the NYC area, has never called me back.  Plus their procedure seems so much more expensive.  I left them a call on Friday anyway.

In light of the fact that I might need to go slow-freeze, I dug deeper into the process, and that only confused me further.  I thought vitrification is clinically proven to be superior, but there isn't enough evidence to prove it one way or the other because the technique is so new.  Is this a medical fad?  Even if vitrification is a superior method, fewer embryologists are trained in it, and I’m apprehensive that it introduces a greater risk of human error. 

All of this hit me very hard that egg freezing is an experimental (says the American Society for Reproductive Medicine), and no one can really provide me with the right answers.  There just isn’t enough evidence to claim one technique over the other, or that either works effectively at all.  And I felt again the difficulty in feeling like I'm navigating this experimental process myself, and that there aren't too many choices in doctors and clinics because very few have a real track record in this space.  

And then I started to get cold feet.

Freezing Process

Here is some info I’ve gleaned about the freezing process (I am not a medical expert and there may be errors in the information below; I’ve used various articles and websites for the information):

There are three steps to the egg freezing process:

1.  Hormone treatments to help the patient produce more eggs
2.  Retrieval of the eggs
3.  Freezing and storing of the eggs

The first two steps are not considered experimental; the same procedures are used for IVF.  The third step is what's deemed experimental by the ASRM.

The egg is the largest cell in the human body, and it contains a lot of water.  Long-term preservation of eggs has been elusive because the formation of ice crystals in the freezing process can destroy the cell.   These days, water is drawn out of the cells and replaced with cryoprotectants (basically “antifreeze”), and then they are frozen (either through vitrification, which is flash-freezing, or using the slow freezing method).  When the eggs are eventually thawed, the cell wall is too hard to allow sperm to penetrate the old fashioned way, so sperm is injected directly into the egg using the intracytoplasmic sperm injection method (called ISCI, also not considered experimental).  

Slow freezing is the method long used for oocyte cryopreservation, and it is the same technique used for embryo freezing.  This technology developed in Europe due to the banning of embryo freezing in Italy in 2004 (since embryos are considered to be human life in Catholicism), and freezing gametes (eggs and sperm) is more acceptable.  Since similar techniques are used for embryo freezing and egg freezing, embryologists and labs are very familiar with the process.

These are the oocyte cryopreservation success rates cited by RMA NY (which I presume are based on slow freezing, especially since the data is a few years old): 

• Over 86% of eggs survived the freezing and thawing process. This is significant achievement as the egg is the largest cell in the body made up mainly of water, which makes it particularly sensitive to damage from freezing.
• Over 90% of thawed eggs achieved fertilization with use of the technique intracytoplasmic sperm injection (ICSI). ICSI is a technique that takes a single sperm and injects it directly into an egg. Due to some hardening of the outer shell of the egg after the thawing process, ICSI is recommended in these cases.
• 92% of fertilized eggs (now embryos) survived to day three, which is when a transfer could take place.

My doctor told me that the hope would be that we get at least 10 to 12 eggs from my cycle.  I've heard of some women getting only a handful of eggs, others yielding 20 or more.  Not every egg harvested is mature and appropriate for freezing.

So the way I interpret this, if 10 mature eggs are harvested in my cycle (which I think is optimistic), then:

• At 86% freeze/thaw rate, 8.6 eggs would survive freezing and thawing.  Let’s round down to eight eggs since you can’t do anything with 0.6 of an egg
• Then 90% fertilization rate = seven fertilized eggs (7.2 rounded down)
• And then another 92% of those, or six eggs (6.4 rounded down), will survive to day 3 embryos
• The implantation rate for embryos from fresh or frozen eggs seem about the same (some say frozen eggs do slightly better, some say slightly worse), and they range from 40% to 46%.  If we apply an average of 43% to the six embryos, that’s about two or three potential implantations* (based on 2.58 rounded up and down)

Vitrification is a newer freezing technique that developed out of Asia.  Higher concentrations of cryoprotectants are added to the eggs, and they are “flash frozen”, and the egg results in what looks like a frozen glass ball.  Early studies seem to indicate that this method results in a higher “rate of return” on frozen eggs, perhaps as high as 90% to 95% survive the freezing/thawing process (as compared to 86% cited by RMA).  Applying these rates to 10 eggs as above,

• If we apply 92.5% freeze/thaw rate, 9.2 eggs would survive.  Let’s round this number down to nine eggs.
• Then 90% fertilization rate = eight fertilized eggs (8.1 rounded down) 
• And then let’s assume the same 92% rate survive to day 3 embryos using ISCI = seven embryos (7.36 rounded down) 
• If we apply 43% implantation rate, then we end up with three potential implantations* 

*In both scenarios, it is important to keep in mind that successful implantation does not necessarily lead to full-term pregnancy and delivery…  

 

Clearly this is very crude arithmetic that oversimplifies a complex procedure with many variables, but this gives you a sense of how vitrification might help eke out slightly better numbers, especially if precious few good eggs are retrieved.

Before I have total buyer’s remorse, I have to remember that I was comfortable with the stats provided to me by my clinic, and I decided to pursue this for myself based on those numbers.  I'm just crossing all my fingers and toes that I have a very productive cycle...