Embryo Cryo Preservation

A cryoprotectant is required to successfully freeze embryos.

Embryos contain a cluster of cells.

Cells contain water. Water expands when frozen.

The expanding water will burst the cells in an embryo if frozen without a cryoprotectant.

Ethylene Glycol and Glycerol are used as cryoprotectants to freeze embryos successfully.

The embryo gets drawn up into a straw surrounded by one of the cryoprotectants. It then gets cooled down slowly inside a special freezing machine. This process dehydrates the embryo and prevents cells from bursting. Embryos are frozen at a rate of 0.5 degrees C per minute until at -35. From here they get submerged in liquid nitrogen and stored for future use. The freezing process takes about one hour.

Embryos can be stored for many years. It seems that the embryo does not deteriorate over time in the nitrogen. This means that embryos can theoretically be stored for 100’s of years.


Make sure when storing embryos that they are submerged under nitrogen and not stored in nitrogen vapour only.