We use a process called ‘vitrification’ to freeze sperm, eggs and embryos. Vitrification involves much more rapid cooling than other less advanced methods of freezing, and it prevents ice crystals from forming. This preserves the quality of the cells and improves the chances of success when they are thawed.
Embryo vitrification is now a well-established procedure. It allows us to freeze any good quality embryos that remain after embryo transfer or if transfer needs to be delayed. Embryos can be frozen at various stages, depending on how they develop. The decision to store embryos will depend on when embryo transfer takes place, and the number of good quality embryos available in the cycle.
Vitrification has improved the outcomes of embryo freezing. It’s now a very reliable practice, yielding success rates as high as those achieved with fresh embryos.
Occasionally, it may be decided to vitrify all the embryos in a cycle and postpone embryo transfer. We do this to help prevent ovarian hyperstimulation syndrome (OHSS). If this is the best course of action for the individual being treated, the embryos are thawed and replaced in a subsequent cycle.
We can use vitrification to successfully freeze eggs immediately after the collection procedure. This is important for women who would like to store eggs before undergoing chemo- or radiotherapy, or other treatments that might affect their fertility in the future.
We also store eggs for women who are not ready to start a family now, but who recognise the importance of storing eggs while they are younger. Eggs collected and stored earlier in life are of a better quality than those women produce later on. Patients who choose to freeze eggs when they are under 35 tend to have higher success rates.
You may need to store sperm for fertility preservation before certain medical procedures or in the course of a fertility treatment cycle:
Prior to chemo- or radiotherapy
Prior to vasectomy
Prior to any surgery that may result in impaired fertility
Prior to a fertility treatment cycle and after sperm has been retrieved via surgery
Prior to a fertility treatment cycle as a ‘back-up’ sample for the day of treatment
Sperm that is donated for other couples or individuals to use also has to be vitrified and quarantined while all the appropriate donor screening tests are conducted. The sperm is not released for use until all test results come back and are clear.