Frozen Embryo Transfer
Freezing is now an essential part of every clinic's IVF programme. In fact, studies have proven that results are better when embryos are transferred in later non-stimulated cycles rather than directly following egg collection. Thanks to improved freezing techniques, clinics across the UK - and across the world - are moving towards freezing all embryos and transferring them at a later date once the female partner's body has returned to normal following stimulation.
This approach is at the heart of the London Women’s Clinic IVF programme which involves freezing all embryos in an IVF cycle and transferring after thawing one at a time in later non-stimulated cycles. This maximises cumulative live birth rates per IVF attempt while minimising multiple pregnancies, which increases the health risks for both mother and baby.
Frozen Embryo Transfer process
Thawed embryos may be replaced during a natural cycle (without drugs) or in a cycle primed with hormone supplements. Depending on your medical history and age, your fertility specialist will be able to discuss with you which treatment will be most appropriate for you.
The frozen embryo transfer itself is the same procedure as an embryo transfer in a fresh cycle. Once the embryo is thawed, a catheter holding the embryo is gently inserted into the cervical channel and into the uterine cavity guided by ultrasound. The catheter is then removed and checked to make sure the embryo has been transferred. After the transfer, you can return to normal with the embryo quite safe within the uterus. Following embryo transfer, a pregnancy test is usually arranged twelve to fourteen days later. During this time, it is best to avoid strenuous activity and heavy lifting.
For most people undergoing IVF or ICSI treatment, there will also be embryos remaining for the future either if treatment is unsuccessful or for a sibling. Spare embryos from your IVF treatment can be frozen for future use, depending on their quality. This would require having a frozen embryo transfer or "FET" cycle. Embryos can be stored for up to ten years for future treatment.
Success rates when using frozen embryos
Success rates when using frozen embryos continue to improve due to advances in freezing techniques. In fact, studies have proven that results are better when embryos are transferred in later non-stimulated cycles rather than directly following egg collection.
Does the length of embryo storage matter?
No. Successful transfers are not dependent on the length of time embryos have been frozen. They are stored in temperatures close to -200 Celsius and will not deteriorate over time. Many people will store embryos for use years in the future when they are ready to start or add to their family, with no effect on their quality or viability. According to the Human Fertilisation and Embryology Authority, embryos can be stored for up to ten years.
Verified live birth rates are available from the HFEA website. Please note that success rates have limitations as the basis for comparison and personal choice. For further advice, please visit the HFEA's advice pages.