The Fertility Guide: The ART Procedures
All about assisted reproductive technology
Cryopreservation of Eggs
In most cases, more eggs are retrieved than can reasonably be used for an ART procedure. If we retrieve 10 eggs, and are only going to transfer three eggs (GIFT) or embryos (IVF), then some decision must be made as to what to do with the other seven eggs. One option is certainly just to discard them since they are not fertilized. They are just eggs, and in an unfertilized state, they may be simply discarded. The other is to cryo-preserve them.
Unfortunately, although techniques for the successful cryopreservation of eggs are being developed, the very poor success rates with this procedure do not yet allow it to be clinically useful. In order to do cryopreservation successfully, the egg must first be fertilized. Once fertilized, cryopreservation is possible at many stages of embryo development, ranging from the zygote all the way to the blastocyst. There are advantages to doing cryopreservation. The first and most obvious is that it provides an additional chance at pregnancy without going through all the medications and without going through another egg retrieval. Cryopreserved embryos are typically returned by a simple embryo transfer in a cycle using no medications, or at most minimal medications. In short, there’s another chance of conception that’s relatively easy and inexpensive.
There is another advantage to doing cryopreservation in the case of an IVF attempt—all the eggs can be inseminated. If one has opted not to do cryopreservation, then only a certain number of eggs can be inseminated because only a certain number of embryos can safely be transferred back to the uterus. For example, if cryopreservation is not an option and only three eggs are inseminated and only two fertilize and develop normally, then the chances of that procedure being successful may be compromised. On the other hand, if cryopreservation is an option, then all of the eggs can be inseminated, three of those that fertilize can be transferred to the uterus, and the remainder cryopreserved. Opting for cryopreservation increases the chances of the procedure being successful as well as offering an additional chance at pregnancy in a subsequent procedure. Cryopreservation is also an option when doing a GIFT or ZIFT procedure.
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