The Basics of Egg Cryopreservation
- Posted on: Jun 28 2014
Oocyte or egg cryopreservation is the process of extracting and freezing eggs until the time is ready for their use. During assisted reproductive technology procedures, the frozen eggs can be thawed out, fertilized in vitro and transferred to the recipient’s womb for pregnancy to ensue.
Egg cryopreservation can benefit women with varied fertility concerns. Women diagnosed with cancer, but have not started treatment, can cryopreserve their eggs for later use. In addition, women who are planning on having a child later on in their lives can freeze their eggs when their fertility is at its peak. Donor eggs can also be preserved using this process to help an infertile woman become pregnant.
Method Development: The challenge for any cryopreservation technique is to maintain the viability of the frozen eggs. Freezing and thawing causes stress on these cells, possibly resulting in cell death, decreased fertilization and impaired embryo development. Slow freezing of eggs has led to modest clinical success. However, recent advances in methodologies for slow freezing has improved overall outcome. Moreover, vitrification, another method of freezing eggs, has shown satisfactory outcomes in recent years.
Advantages: There are several advantages to egg cryopreservation for egg donation cases. If a donor egg bank is available, a recipient can choose from a large pool of donors. Egg bank facilities can give the recipient a selection of healthy, rigorously-screened donor candidates. From the convenience of their homes, a recipient can search the online donor catalog to select a suitable match.
This shortens the waiting times involved in finding a match. Moreover, the hassle of planning and working with the schedule of a fresh egg donor is eliminated. Unexpected events, such as medication errors or non-compliance by the donor, can occur in fresh egg donation cases. Recipients can avoid these inconveniences by choosing from the frozen egg bank.
Previously, the egg retrieval process for egg donors had to be synchronized with the uterine preparatory process of the recipient. With the availability of cyrobanks, the donor eggs can be stored for 6 months or longer. The process of in vitro fertilization (IVF) would be initiated once the recipient is prepared for the transfer. The egg donor does not have to schedule her activities around the timings of the recipient.
Several recipients can use cryopreserved donor eggs, and therefore, the treatment becomes more affordable to individuals. Moreover, by using a cryobank, a recipient may choose to use reserved donor eggs from the same donor in the future.
Any unused, excess embryos during IVF procedure can now be frozen (cryopreserved) for later use by the recipient. This prevents the wasting of viable embryos and saves costs borne by the recipient.
Risks: Egg cryobanking is more efficient, safe and affordable as compared with fresh oocyte donation. Although the efficiency of using frozen eggs for IVF is at par with that from fresh eggs, there exists a marginal risk of losing cell viability from the freeze / thaw cycle. This could result in a negative pregnancy test, or miscarriage. However, the overriding advantages and impressive success rates of frozen eggs in IVF treatment makes cryopreservation an attractive alternative to consider.
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