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Frozen Embryo Transfer

For most people undergoing IVF or ICSI treatment, there will be embryos remaining for the future either if treatment is unsuccessful or for a sibling.  This would require having a frozen embryo transfer or “FET” cycle.

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. 

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.

One by One IVF

This approach is at the heart of the London Women’s Clinic pioneering One by One IVF programme that is only available at a handful of top clinics worldwide so far.   One by One IVF is an innovative, new programme which involves freezing all embryos in an IVF cycle and transferring after thawing ‘one-by-one’ 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.

Spare embryos

Spare embryos from your IVF treatment can be frozen for future use, depending on their quality. Embryos can be stored for up to ten years for future treatment if your first cycle was unsuccessful or for siblings.

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.

Success Rates

Up to 35

Pregnancy rate per embryo transferred

June 2015 - July 2016

National average 36%

36-37

Pregnancy rate per embryo transferred (based on 43 cycles)

June 2015 - July 2016

National average 31%

38-39

Pregnancy rate per embryo transferred (based on 44 cycles)

June 2015 - July 2016

National average 24%

40-42

Pregnancy rate per embryo transferred (based on 48 cycles)

June 2015 - July 2016

National average 18%

Three Cycle Package

Package completed June 2015 - July 2016

All ages

No national average available

Up to 35

Pregnancy rate per embryo transferred

June 2015 - July 2016

No national average available

36-37

Pregnancy rate per embryo transferred

June 2015 - July 2016

No national average available

Over 38

Pregnancy rate per embryo transferred (based on 45 cycles)

June 2015 - July 2016

No national average available

All ages

Pregnancy rate per embryo transferred (based on 48 cycles)

June 2015 - July 2016

No national average available

Egg share donors

Pregnancy rate per embryo transferred (based on 27 cycles)

June 2015 - July 2016

National average 44%

Donor egg recipients

Pregnancy rate per embryo transferred

June 2015 - July 2016

No national average available

All ages

Pregnancy rate per embryo transferred (based on 17 cycles)

June 2015 - July 2016

No national average available

All ages

Pregnancy rate per embryo transferred (based on 43 cycles)

June 2015 - July 2016

National average 15% (all ages)

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.  

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