Egg Freezing

A somewhat new development to the field of assisted reproductive technology that is still in the investigational stages is oocyte (or egg) cryopreservation. Most commonly, egg freezing is being employed by single women about to start cancer treatment known to affect ovarian function, as well as women who desire to preserve their future fertility. While many factors can affect a woman’s ability to become pregnant, her age is probably the most important one. As women get older, their chance of conceiving declines (see age and infertility). For this reason, many women are choosing to freeze and store their eggs for future use.

Oocyte cryopreservation, like IVF, requires ovarian stimulation with injectable fertility medications followed by a procedure called an oocyte retrieval whereby the eggs are collected. Oocyte cryopreservation differs from IVF in that the mature eggs are not fertilized but rather frozen for future use. One of the main obstacles in oocyte cryopreservation has been the fact that oocyte freezing/thawing can be technically challenging.

The mature egg is extremely fragile due to its large size, water content and arrangement of chromosomes. An additional challenge with this technology has been lower than expected fertilization rates upon thawing. The outer shell of the egg, the zona pellucida, has been noted to harden in the process of oocyte cryopreservation, necessitating ICSI to help overcome this issue.