The purpose of egg cryopreservation (freezing) in an Assisted Reproductive Technology (ART) program is to preserve unfertilized eggs, for fertilization and uterine replacement at a later time. This procedure has the potential to be beneficial to patients desiring to preserve fertility. Egg freezing can be performed prior to chemotherapy, radiation, surgery that might render a woman infertile or for advancing maternal age in a woman who is single or for a woman who desires to delay fertility for career or other reasons.
Egg freezing also has the potential to be used for cryopreservation of donor eggs so that multiple recipient couples could use eggs from the same egg donor without the need for endometrial synchronization and preparation of all female recipients at the same time the eggs are retrieved.
Freezing extra eggs when a large number of eggs are retrieved from an egg donor allows couples the option of donating unused and unfertilized eggs to other infertile couples while maintaining the option of using the eggs themselves if the initial in-vitro fertilization (IVF) fresh cycle does not result in a pregnancy, or when additional pregnancy(s) are desired at a later time. The option of freezing eggs eliminates the need to fertilize too many eggs that may result in extra embryos that may not be used or needed.
Patients and reproductive biologists have had a tremendous interest in egg freezing for several decades. The difficulty in the past is that eggs that were frozen had a poor survival rate and those that did survive often did not fertilize due to hardening of the shell of the egg. The fertilization issue was primarily solved in the mid-nineties with the advent of intracytoplasmic sperm injection (ICSI). The egg survival issue has required years of research and development in order to achieve major improvements. This research has improved remarkably in the past few years. IVF programs in countries such as Italy now routinely freeze any eggs retrieved greater than three due to local laws. These programs have had excellent success at improving pregnancy rates as these techniques have improved.
The difficulty with egg freezing is that the delicate oolema (egg cell membrane) must not rupture during freezing and ice crystals must not form in the cytoplasm of the cell. Ice crystals can destroy the cytoskeletal structure of the egg eliminating the possibility of successful freezing.
The membrane surrounding individual cells of embryos is “stronger” which is why successful embryo freezing (cryopreservation) has been available at Reproductive Care Center for years. Cryopreservation of embryos is offered as a routine part of an IVF cycle when there are excess embryos.
Recent improvements in slow freezing protocols (LANDA method) and the refining of a process known as “vitrification” has helped open the door to successful egg freezing technology. In the vitrification process, the egg cells are stabilized in various cryoprotectants until equilibrium is reached. The eggs are then placed directly into the “freezing medium” which is liquid nitrogen vapor, and frozen instantly. This rapid freezing avoids the formation of ice crystals that would destroy the fragile egg cells.
The survival rates of eggs frozen using vitrification or the newer slow freeze technique are far higher than older conventional methods. Our laboratory personnel have experience using both the new slow freeze and vitrification techniques. Reproductive Care Center is the only infertility clinic in Utah licensed to use the LANDA egg freezing protocols and methods.
The success rate per cycle using embryos from fertilized eggs that have previously been frozen is usually lower than from the IVF success rates of transfer of fresh embryos (embryos created from eggs that have not been frozen). The overall success rate depends on the age of the woman when the eggs were formed, the egg quality and maturity, the status of the egg at thaw, the quality of the embryos formed and any other factor that would otherwise influence IVF success. Survival of the egg can be variable but has been reported as high as 90% based on numerous studies.
Recent optimal success rates per cycle are reported to be in the 30-40% range or higher per embryo transfer. According to the American Society of Reproductive Medicine (ASRM), based on published peer-reviewed medical literature there is an approximate overall 2% live-birth rate per oocyte thawed for cryopreservation using the older slow-freeze methods. There is an approximate overall 4% live-birth rate per oocyte thawed for cryopreservation using vitrification. However, pregnancy rates as high as 8% per frozen egg (on average 12.4 eggs needed per pregnancy) have been achieved at centers using some of the newer freeze methods such as LANDA.
Although ASRM still considers egg freezing “experimental” as the success and pregnancy rates have improved, many fertility clinics in the country have implemented egg freezing as a part of their services. In several of these programs egg freezing is used in the donor egg program to facilitate cycle synchronization.
If a woman decides to proceed with egg freezing, after informed consent, the eggs are retrieved after ovarian stimulation with fertility drugs, such as follicle stimulating hormone (FSH, Gonal-F, Follistim, Bravelle, Menopur, etc.). These drugs cause the ovary to produce multiple eggs as ovarian follicles are directly stimulated by FSH. The eggs are then frozen for use. When a woman decides that she is ready to pursue a family, she returns to the fertility clinic and undergoes an IVF cycle using her frozen eggs. A healthy woman can support a pregnancy well into her late forties and early fifties. The main limiting factor to pregnancy in older women is poor egg quality which is hopefully avoided by using her frozen eggs.
Egg freezing is a relatively "new" procedure so questions about its effectiveness will remain for some years. For example, we don't have the clinical experience to predict how long frozen eggs will remain viable. We assume based on data from procedures such as embryo and sperm freezing, and other fields where frozen tissue is used, that the eggs will most likely remain viable for a patient's reproductive life span and longer. In order to gather more information, RCC is currently requesting that patients participate in a registry (Hope Registry sponsored by EMD Serono) that tracks the outcome of thawed eggs and the outcome of the children born from the pregnancies achieved.
Our fertility specialists have followed egg freezing research closely over the past decade. Dr. Blauer was first involved in research using frozen donor eggs in 1998. The first embryo Dr Blauer transferred using frozen eggs was performed in 2005 while in Virginia. Since then the program he was involved with in Virginia has achieved a number of delivered pregnancies with the use of frozen eggs. The first embryo transfer using frozen eggs in Utah was performed by Dr Heiner at Reproductive Care Center in early 2009.
If you reside in Utah and would like more information about this exciting, but currently experimental, technology please call our office to schedule an appointment with a physician. Currently significant financial discounts are offered for participation in this research.