A Few More Things You Should Know About Egg Freezing and Thawing
Posted Mar 04 2010 3:51pm
Once again, some of this also applies to regular IVF.
Just as not every follicle gives up an egg, not every egg we get is usable. This mostly has to do with egg maturity. We can’t use an immature egg, it will not fertilize later. For those of you familiar with in vitro egg maturation (IVM), I don’t want to get into that whole thing here. Suffice it to say, IVM had a very limited role with very limited success.
Basically, getting an egg to mature after we retrieve it is of little value, we count on the eggs to mature in the ovary before we get them. We need tree-ripened fruit.
Most retrieved eggs are mature but 10-20% may not be. So if say you get 15 eggs, having 3/15 immature is typical. Like anything else we talk about, variations exist. Some women, no matter how we change their drugs or increase the number of days on drugs, end up with ½ or more of their eggs immature. This is an exception, as is the case when every egg is mature.
Less often we have another small problem: atretic eggs. Atretic eggs are basically just dead eggs. This is much rarer than immature eggs. Another rare problem is a cracked zona (cracked shell). These also are not very viable.
So the point here is that if your doctor sees 15 follicles it does not mean there are 15 eggs to use. By the time you account for eggs that don’t get retrieved, immature and atretic eggs and eggs with cracked shells, you should still be left with about10 that are usable. But it could be more or less depending how the chips fall.
And away they go, into the deep freeze, for months or years (decades?. You work, you live and then one day you decide the time has come to attempt pregnancy; you go to the bank and make your withdrawal. This is another spot for potential attrition.
Not every egg survives the thaw, but most do. One of the many really nice papers on egg freezing recently published by NYU’s own Drs. Grifo and Noyes ( Fertility and Sterility Volume 93, Issue 2, 15 January 2010, Pages 391-396) shows that about 92% of eggs survive the thaw. If they survive we can attempt fertilization.
There are 2 ways to fertilize eggs, one is to mix the eggs and sperm together and let the sperm swim in: this is used when the sperm counts and motility are close to normal. The other is, under the microscope, to pick up a sperm and inject it into the center of the egg: this is used when the sperm counts and/or motility is low. This is called ICSI (inter cytoplasmic sperm injection). For some reason, eggs that have been frozen require ICSI to develop into good embryos. The requirement for ICSI is not a big deal; it seems to work quite well, although it does add to the cost of the procedure. But to continue with a familiar theme, not every egg that has ICSI fertilizes. The same study above shows that 79% of eggs that get ICSI normally fertilize, which is very similar to the rate for fresh eggs.
So the 10 that were frozen are now fewer. You could have 10, but the number may be more like 9, 8, 7, 6, or even 5. And we’re not done yet.
Fertilized eggs need to grow in the lab for another 2-4 days before the transfer. I have a number of blogs that describe embryo and blastocyst development, starting on December 14, 2008. There you will see the changes that take place as things progress from egg to embryos as the the days in culture. You can see the difference between good and bad embryos. Naturally you would like to have nice good looking embryos. And as the story goes, not every fertilized egg makes it to a nice embryo.
Reading this one would think that it’s impossible to have a good outcome from egg freezing, but in reality most women have an average egg yield and enough nice embryos to have an average chance for pregnancy. But again, there is variation. The luckiest women have high egg number high fertilization rates and many really nice embryos, and even some extra embryos for freezing. In other scenarios, there are many eggs and embryos, but they do not develop well.
There is a bit of a waiting game to get your results. In fresh IVF, you know within a few days where you stand. With egg freezing, you will not know how many good embryos you have until you thaw the eggs maybe years later.
We do not yet know how many eggs we will need to thaw later. We may feel comfortable enough to thaw 4-6 and try with those. However, as we accumulate more data, we may find that you need to thaw more to have a good chance. This is important because if you have 8 eggs frozen, thawing 4 at a time can give you 2 chances, but thawing all 8 will give you only one. And then there will be a question about how many embryos to put in your uterus, the recommended number may change with time so this is just something to keep in the back of your mind.
Here’s another question. Should you do any “fertility” or “preconception” workup prior to freezing your eggs? The question here is should you have any tests that may effect you ability or decision to get your eggs/embryos back later. For example, should you have a hysterogram to look for abnormalities in your tubes or uterus before egg freezing? Should you have any genetic tests, cystic fibrosis for example, before freezing your eggs? This you should you discuss with your doctor. In actuality, there are very few things that would keep you from getting your eggs back later. If you are a carrier for cystic fibrosis, you probably will still want to become pregnant with your eggs, providing you screen your partner or donor. If you doctor is minimally good at ultrasound, she should be able to tell you if you have a major abnormality of your uterus without a hysterogram. Most women are still candidates for pregnancy even with an abnormal uterus. However, this is very important to review your history and the potential tests with your doctor. I have had women who wanted to have all the tests done before egg freezing, but not everyone does.
Costs. There are a number of cost centers associated with an egg freeze cycle. There is the cost of the egg freeze cycle. This is the fee that the IVF center charges for the ultrasounds and blood tests associated with your cycle. It includes the retrieval procedure and the egg freezing.
What does in not include? You first need to see the doctor and he usually performs an ultrasound. This is separate. There are the optional tests described above, but there are mandatory blood tests that check your thyroid, prolactin, hepatitis status and others. Your insurance may be more likely to pay for theses but you need to check.
You will most likely need anesthesia for your retrieval procedure; in many cases this this is an extra fee of $1000 or more.
There are also yearly charges to store your eggs, which usually kick in after the first year.
Plus there are real costs, in the thousands, associated with getting your eggs back. This requires the thaw, lab handling, ICSI, ultrasounds, blood tests and the embryo transfer. If you have extra nice looking embryos, you may be allowed to freeze some of them, but again there is an extra cost, and a thaw transfer cost again.
OK, I think that's almost everything you need to know about egg freezing. I hope it helps.
Thanks for reading, and read the disclaimer 5/17/06. Looks like spring may finally arrive.