Vitrification is  a physical process by which a highly concentrated solution of cryoprotectant solidifies into a glassy vitrified state from the liquid phase by an extreme elevation in the viscosity while cooling at a low temperature. The solid which is called glass retains the normal molecular and ionic distribution of liquid state and can be considered to be an extremely viscous supercooled liquid. The process avoids intracellular and extracellular ice formation. It thus avoids the possible damage which can be caused by intracellular ice formation and the osmotic effects related to extracellular ice formation.

After a fresh embryo transfer, good quality surplus embryos and blastocysts created during IVF or ICSI treatment may be frozen and stored for future use.  Embryos can be stored at an extremely low temperature (-196˚C) to suspend their development.  Once frozen, they can remain in liquid nitrogen for many years without deterioration before being thawed and, if they survive and subsequently develop well, transferred to the woman’s uterus during a frozen embryo transfer (FET).

Freezing good quality embryos offers a chance of conceiving after an unsuccessful fresh embryo transfer, or even several years following a successful transfer and pregnancy.

Couples, who achieve many good quality embryos following egg collection and fertilization which can be stored for possible future attempts to conceive. A woman in a relationship about to undergo medical treatment that may make her infertile in the future can have embryos created and frozen before the treatment to give her the chance of having children with her current partner, at a later date.patients who have had an egg collection for IVF or ICSI treatment.

Woman who have been advised not to go ahead with a fresh embryo transfer will have their embryos frozen for use in treatment a later date.