There are two types of FET treatment.
Natural Cycle FET:
This is used for those who have regular cycles and ovulation. Embryos are transferred after a positive ovulation test.
Programmed Medicated Cycle FET:
In a programmed FET you take medication, usually Oestradiol tablets to grow the lining of the womb until such a stage they are ready to receive embryos for implantation. This is followed by progesterone pessaries to support implantation and development of the baby until 12 weeks of pregnancy.
Frequently Asked Questions
How long can blastocysts be stored?
UK law permits blastocysts to be stored for up to 55 years. Freezing stops all activity in the blastocyst cells. This means that the blastocyst does not age and success rates will be in line with your age at the time the blastocyst was stored, regardless of when the thaw and FET takes place.
How do you thaw embryos?
On the scheduled day of FET, the device containing the blastocyst is taken out of the liquid nitrogen and rapidly warmed to 37oC before being washed through a series of solutions to help it to recover. In the hours that follow, the blastocyst should return to its original state ready to be transferred.
What proportion of blastocysts survive the thawing process?
The freezing and thawing processes are not without risk and in a small percentage of cases the blastocyst does not survive the thaw. We have refined our techniques over a number of years, and we have excellent survival rates of over 97% for good quality embryos. However, lower quality blastocysts, which did not meet the laboratory criteria for freezing, have a lower chance of survival.