One of the hot topics in the fertility field is Egg Freezing, and, once perfected this technology could revolutionize the field of reproductive medicine. It could allow a woman to freeze her eggs and, at a later date, those eggs would be thawed, fertilized, and transferred into her uterus in order for her to conceive. The potential benefits of this technology are substantial. For instance, it could allow a young woman embarking on her career to delay motherhood until she was ready to conceive, thus circumventing age-related fertility factors such as decreased ovarian reserve. Additionally, egg freezing could benefit women undergoing chemotherapy (which can render a woman infertile) as the eggs are retrieved and frozen prior to chemo. Egg freezing, however, is still in its infant stages (no pun intended) and is used in limited cases…primarily for women undergoing chemo. Nevertheless, it’s promising to note that more and more fertility clinics are pursuing egg freezing. In fact, where I practice, our IVF laboratory is involved in a research project working with the technology of the egg freezing process. When my physician colleagues and I feel that the results are sufficient to offer our patients such a service, we plan to add this procedure to our services.
As background, eggs are very delicate. They are the largest cell in the body and contain a great deal of water. In order to freeze eggs the water must be extracted and replaced with an anti-freeze type solution. Water expands when it is frozen, so if the water is not replaced before freezing, the expansion can cause the cell to burst. Once the water is removed there still remains an issue with the egg's chromosomes. Just prior to ovulation the chromosomes of the egg line up on "spindles." Half the chromosomes separate and move out of the cell in a “polar body” and the other half of the chromosomes remain organized on the spindles to be matched up with the sperm's contribution. The spindles are very delicate and subject to changes in pH, temperature, etc. When the egg is frozen and thawed what frequently occurs is that the spindles break apart and the chromosomes are dispersed randomly throughout the egg. When the time comes for the egg to be fertilized, the egg must organize the chromosomes to meet up with the sperm's contribution. The egg is not well equipped to do this reorganization and often there are resultant chromosomal problems. These chromosomal problems affect the ability of the embryo to fertilize and to continue into an ongoing pregnancy. The pregnancy rates of an embryo created from a fresh egg and sperm and then cryopreserved are much better than the success rates of an embryo created from an egg that has been previously cyropreserved. Currently the PFC lab freezes embryos. We have had good success with pregnancies from cyropreserved embryos.
Nevertheless, we are enthusiastic about our ongoing egg freezing program and the ultimate benefits that it could provide to patients with and without an infertility diagnosis.
For more information on this topic, please drop me a line. I also recommend you read the article written by my colleague, Joe Conaghan, Phd, Pacific Fertility Center Laboratory Director, which is titled “Oocyte Freezing Hype.”