Embryo Cryopreservation

Embryo Cryopreservation is the process by which the surplus embryos from an IVF or ICSI cycle may be stored or frozen, for use at a later date.

Embryos can be frozen at a number of their developmental different stages –up to and including blastocyst stage. The Embryologist selects the embryos suitable for freezing. The embryos are then introduced into special culture media, called cryoprotectant, to help protect them during the freezing and storage process. The embryos are then frozen using a computerised embryo freezer.

Once frozen, the embryos are contained within appropriately labelled sterile straws. These straws are then securely stored in a locked storage vessel immersed in liquid nitrogen ( - 196o C). Embryos can be safely stored like this for up to 5 years.

Embryo Thawing is the process by which frozen embryos are thawed with a view to replacing the most suitable into the woman’s uterus. The freezing and thawing of embryos allows patients use surplus embryos from previous cycles.

During thawing, the frozen embryos are warmed in a controlled manner. Once thawed the embryos are introduced back into embryo culture. The embryos are thawed the day before the embryo transfer in order that the embryo’s development can be monitored. Not all embryos survive the freeze/thaw process.

Our Fertility Specialist performs the embryo transfer procedure. The selected embryos are introduced, through a fine catheter, into the woman’s uterus. Typically 2-3 embryos are transferred, depending on the patient’s circumstances. The embryo transfer procedure takes no more than half an hour and few women experience any discomfort.

Again, the spare embryos are then assessed in terms of their suitability to be re-frozen for use, by the couple, in future cycles.

Worldwide, the success rates for frozen-thawed embryos are lower than those for fresh embryo transfers.