Why freeze embryos?
When you undergo your IVF treatment you may find that as well as having a suitable number of embryo(s) for transfer that there are some extra embryos that are then suitable to be frozen.
Freezing embryos for future fertility treatment avoids the need of going through another round of IVF treatment. If your treatment with the fresh embryos is successful these frozen embryos can be used as a future dates to provide your child with a biological sibling.
How are embryos frozen?
The cryopreservation process uses a series of specially designed solutions that work to quickly dehydrate and stabilise the embryos before they are plunged directly into liquid nitrogen; this is known as vitrification. Dehydration is necessary to prevent ice crystals forming in the embryo during freezing.
Embryos are stored in small containers that hold a maximum of two embryos. This is followed by storage in large tanks of liquid nitrogen at minus 196 degrees Celsius. All tanks are fitted with alarms that notify us 24 hours a day of any change in temperature that may require our attention.
Will my embryos be frozen?
Only the best grade embryos have the potential to withstand the freezing process, which is somewhat stressful to the cells. We expect an average 90% of embryos to survive freezing and thawing.
If there are good quality embryos remaining after your fresh embryo transfer, we will continue to culture the remaining embryos to the blastocyst stage of development prior to freezing. Any good quality blastocysts that have developed can be frozen (cryopreserved) for future use.
Embryo freezing should be regarded as a bonus: only about half of couples will have embryos frozen in any one treatment cycle.
How successful is freezing embryos?
Pregnancy rates for frozen embryos transfers are slightly lower than for fresh embryo transfers, but depend on the number and quality of embryos frozen. Typically they are about 30% per embryo transfer for patients under 40.