Long term IVF embryo storage in the UK relies on liquid nitrogen cryogenic preservation at minus 196 degrees Celsius. At this temperature biological activity stops entirely, meaning embryos can remain viable indefinitely provided the cold chain is never interrupted.
The process begins at the point of freezing. Embryos are loaded onto vitrification carriers or into storage straws, cryoprotected to prevent ice crystal formation, and then plunged into liquid nitrogen either through vitrification (rapid freezing) or slow controlled rate freezing. They are then transferred into cryogenic dewars — vacuum insulated storage vessels — where they remain until the patient is ready to proceed with a frozen embryo transfer cycle.
Maintaining long term storage safely requires three things: an uninterrupted liquid nitrogen supply, continuous automated temperature and level monitoring with 24/7 alarm systems, and permanent reliable sample identification on every stored unit. That last point is more critical than most clinics initially appreciate. A label that fails after five years of liquid nitrogen storage leaves a sample permanently unidentifiable. Standard permanent markers crack and fade in cryogenic conditions. UK fertility clinics use purpose built cryogenic labelling supplies from Cryolab.co.uk to ensure identification remains intact across the entire storage period.
