Spare embryos from your IVF treatment can be frozen for future use, depending on their quality. Frozen cycles are necessary for those wishing to use their previously stored embryos.
With a stimulated frozen cycle, patients take medication to go through the process of down-regulation. This temporarily shuts down your ovaries and prevents any eggs from being released. You will have a scan and then start taking medication to prepare your womb for the embryo transfer. A second ultrasound scan around day ten will be performed to check the thickness of your endometrium. Once it is of the appropriate thickness we can start the embryo thawing process and book your transfer.
Sometimes we may suggest a natural frozen cycle where there is no down-regulation phase. We sometimes use some medication to help the lining to thicken. A scan will be booked for around day ten. If the lining does not thicken sufficiently we can then convert to a stimulated cycle.
Embryos are thawed in the laboratory and assessed as to whether they have fully survived the thawing process. Our embryology team will inform you of how well your embryos have survived and if they are of good enough quality for your transfer to take place. Sometimes embryos do not survive the thawing process. If this is the case, you will be offered a follow-up appointment with one of our consultants to discuss the results and further options.
Hopefully the embryos will then be ready to transfer as in a fresh cycle. Our frozen cycle success rates have been improving year on year and are now almost as high as our fresh cycle rates.
We find approximately 80% of frozen embryos survive the freezing/thawing process. This can vary depending on what stage of development the embryos were at when they were frozen, and the effect freezing may have on different embryos.
Frozen embryos are stored in liquid nitrogen at a temperature of -196°C. This means they are held in a suspended state and do not deteriorate with time in storage.
Our aim is to give you the best chance possible of pregnancy with each frozen embryo replacement cycle. Not all embryos have the same potential to form a pregnancy, and each one is affected differently by the freeze and thaw process. We will have a discussion with you as to how many embryos to thaw.