Embryos can be frozen as part of a standard IVF cycle where any excess embryos of good quality not transferred are frozen or they can be frozen as a stand-alone process for later use for fertility preservation purposes.
Treatments using frozen embryos at the Lister Fertility Clinic have now produced over 1300 babies.
Any embryos frozen can be thawed and transferred in a future cycle that is a much simpler process. Often this involves only monitoring of a natural cycle for ovulation at which point embryo thaw and transfer can be appropriately timed (without the need for significant drug treatment or the invasive collection procedure.) If the woman's cycle is irregular we may recommend hormone replacement therapy (HRT), which will allow us to prepare the lining of the uterus for frozen embryo transfer.
Patients are also responsible for keeping in touch with The Lister Fertility Clinic and notifying us of any change of address. The storage period is governed by law and we do not need your consent to remove these embryos from storage at the completion of the statutory period.
Embryo freezing post IVF embryo transfer
Following embryo transfer on Day 5-6, any extra blastocysts of top quality can be cryopreserved and stored for up to 10 years for future use. Due to our careful selection of only what we deem suitable for freezing, these embryos have >90% thaw survival rate.
Embryo freezing as fertility preservation
As there is a longer history of success with embryo freezing than egg freezing, women within a relationship may opt to undergo ovarian stimulation as for a standard IVF cycle, fertilise eggs with partner sperm and store these embryos for later use. This may offer her a better chance of a successful pregnancy in the future than using her older "fresh" eggs, which may be lower in both quality and quantity. In this scenario, where we are not aiming to select and transfer the best embryo they are frozen at the "2PN- stage", i.e. the day after egg collection.
How successful is embryo freezing?
Although historically frozen embryos are suggested to have lower success rates, the difference with fresh is now questioned. Recent studies suggest that if you directly compare top quality fresh and frozen, the frozen embryos may in fact yield a better pregnancy outcome, along with a lower chance of obstetric complications such as preterm labour and fetal growth restriction