Cryopreservation is the process where embryos are preserved (frozen). Embryos are drawn up into straws and loaded into a cryo chamber of the cryo bath. The cryo machine is temperature controlled and freezes at the gradual rate to ensure steady crystallization. After the cryo machine reaches -35°C, the embryos are plunged into liquid nitrogen at -196°C and stored in long-term storage tanks until transfer or export date. Embryos can be stored indefinitely at these conditions, with very little or no change in conception due to long storage.
Embryo quality when freezing is very important, with grade 1 embryos having the best chance of development after thawing and transfer. Grade 1 and 2 embryos preserve well, but it is preferred to transfer both grade 2 and 3 embryos fresh. Grade 3 embryos do not freeze well and conception rates are low.
With IVF embryo production we preserve blastocyst embryos with a three-step freezing protocol. The advantages of the media we use, is that the IVF embryo can be thawed and transferred directly with decent results. Only grade 1 embryos are selected for preservation or fresh transfer.
Embryo preservation after flushing is a much easier process with a one-step freezing media, with direct thaw and transfer. It is important to use the correct thaw protocol, depending on media and protocol used during the freeze process.