Vitrification of human oocytes and embryos: An overview

Vitrification is the achievement of a state of suspended animation wherein molecular translational motions are arrested without structural reorganization of the liquid. Vitrification protocols are relatively simple for the practitioner, potentially faster, and inexpensive. The process relies on the placement of the cell in a very small volume of vitrification medium that must be cooled at extreme rates, which are difficult to obtain in regular enclosed cryostraws or vials. The growing number of reports of successfully completed pregnancies following vitrification makes for an extremely encouraging future for its wider adoption, the procedure appears safe, is easily assimilated into a busy IVF laboratory, and promises improved patient outcomes when used correctly. For blastocyst vitrification, a closed system is effective for achieving high implantation and pregnancy rates as seen with fresh embryo transfers. With this increased use of vitrification in human-assisted reproduction, we should see an evolution of the vitrification process as it is fine-tuned to clinical needs. Thus, the future should bring higher levels of clinical efficiency, utilization, and universal acceptance.