The technique of freezing embryos for storage is called cryopreservation and the first birth after freezing was recorded in the 1980s. Its contribution to IVF treatments has been increasing ever since.
Traditionally, in the practice of IVF, a handful of embryos are formed and the best is freshly replaced into the womb and the rest are frozen to be used at a later date, either if the first embryo does not result in a successful pregnancy, or if further pregnancies are desired. There is a pool of research accumulating suggesting freeze-thawed embryo transfer (FET), which involves freezing all of the embryos rather than replacing the best fresh embryo, may result in better pregnancy outcomes. The kind of beneficial outcome discussed include:
- Avoiding low birth weight and prematurity which can lead to further problems as the child develops
- Birth defects to do with the heart, digestive system, urinary and/or gynaecological system, and muscle and/or bone system, and also cerebral palsy
- Fewer problems with bleeding prior to labour or placenta abnormalities
- Decreasing risk and progression of late onset ovarian hyperstimulation syndrome (OHSS), which is an uncomfortable and potentially dangerous complication of ovarian stimulation
How is Freeze-thaw Embryo Transfer (FET) different?
FET is a process to preserve embryos not replaced immediately after fertilisation, by freezing and storing them in liquid nitrogen. These embryos are now called cryopreserved embryos and can be replaced at later date. The embryos are cryopreserved using a method called vitrification, which the embryologists at the Reproductive Health Group at used for long time.
Once thawed, these embryos can be replaced into the womb, at an appropriate stage of the cycle, when there is a more natural environment available compared with a fresh transfer where the hormones from ovarian stimulation may have altered the favourable conditions. If you opt for a freeze all cycle, you can choose to transfer the embryo(s) at any time.
What do we do at the Reproductive Health Group
The consultants and embryologists at the Reproductive Health Group will discuss the available options with you and your partner, and recommend the best approach for your treatment cycle. Decisions to freeze all embryos are made case by case, depending on previous history, findings in the fresh cycle and availability of suitable embryos. One in two patients undergoing a FET cycle at the Reproductive Health Group achieve a clinical pregnancy.