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. Some patients have had babies more than ten years after their embryos were originally created and frozen. Under controlled conditions, embryos are cooled and stored at extremely cold temperatures (-196°C) which suspends their development. Once frozen, embryos can remain in liquid nitrogen for years without deterioration before being thawed and, if they survive and develop well, transferred to the woman’s uterus during a frozen embryo transfer [FET].
Using thawed frozen embryos gives the possibility of a brother or sister for a patient’s baby from a single cycle of IVF or ICSI treatment.
Suitable embryos are placed in labelled straws in cooling solutions and then stored in tanks of liquid nitrogen at -196°C. To be suitable to freeze, embryos must:
Embryos may be frozen at various stages of development:
Embryos are stored in cryocans at CARE IVF which are regularly inspected
Legislation determines the time that CARE IVF, with patients’ consent, is allowed to store embryos. Currently embryos may be stored initially for 10 years. Under exceptional circumstances, storage may be extended up to 55 years from the date of freezing (to be reviewed every 10 years), if the patient, partner or someone to whom the embryos are allocated is prematurely infertile or likely to become prematurely infertile.