ABSTRACT
Decades ago, most assisted reproductive technologies including in vitro fertilization (IVF) and cryopreservation of embryos by traditional freezing were applied to humans almost immediately after the first successes in some exper- imental or domestic species. However, there are some techniques where efforts to adopt a new approach were insufficient and sporadic, and consequently the practical application has been considerably delayed. Vitrification belongs to the latter group. Reasons for this delay may include the fact that cryopreservation of zygote-, cleav- age-, and blastocyst-stage human embryos was more or less resolved by traditional freezing; vitrification has and still uses a seemingly very “undeveloped” manual technol- ogy compared to automatic traditional freezers and stan- dardized, ready-to-use media. The high concentrations of cryoprotectants required for vitrification discouraged some potential users initially. Finally, none of the major suppliers were eager to replace their expensive freezing machines with the much simpler system required for vitri- fication (though very recently there have been some efforts to develop an instrument that would allow a “semi-auto- mated” vitrification process [1]).
