What is cryopreservation and how does embryo cryopreservation work in an IVF laboratory?

Cryopreservation is the process of cooling biological material to sub-zero temperatures to halt all metabolic activity and preserve cellular viability indefinitely. In clinical practice, the term covers the freezing and long-term storage of embryos, oocytes, sperm, and tissue samples at temperatures typically reaching minus 196 degrees Celsius using liquid nitrogen as the primary refrigerant.

Embryo cryopreservation specifically refers to the preservation of fertilised eggs at the blastocyst or cleavage stage following in vitro fertilisation. According to the Human Fertilisation and Embryology Authority (HFEA), over 2.5 million embryos are stored in the United Kingdom at any given time, reflecting the central role cryopreservation now plays in IVF practice. The two established methods are controlled rate freezing, which follows a defined programmable cooling curve, and vitrification, which achieves ultra-rapid cooling rates exceeding 20,000 degrees Celsius per minute to form a glass-like amorphous state without ice crystal formation.

Vitrification has become the dominant clinical method for embryo cryopreservation because it eliminates the mechanical cell damage associated with ice crystal nucleation. Research published in Reproductive BioMedicine Online consistently demonstrates superior post-warm survival rates using vitrification compared to slow-freezing protocols across oocyte, cleavage-stage, and blastocyst cohorts.

The cryogenic chain for embryo cryopreservation requires a vitrification system, appropriate carriers such as closed high security straws, storage dewars operating at minus 196 degrees Celsius in liquid phase or minus 150 to minus 180 degrees Celsius in vapour phase, and organised racking systems to maintain sample traceability. Cryolab supplies the complete cryopreservation equipment chain to IVF clinics and sperm banks across the UK and internationally, including CBS high security vitrification kits and the CryoNest dewar range engineered for stable long-term embryo storage. Full product details are available at cryolab.co.uk.