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.