Sperm and embryo freezing (cryopreservation) and storage

Key benefits

  • Sperm freezing and storage can performed as a back up to using fresh sperm, such as when a husband’s work commitments prevent him from being available to provide a fresh sample. It also a useful backup technique for husbands who may find it difficult to produce a sample on the day of egg pick-up.
  • After a stimulated ART cycle there may be surplus embryos. These can be cryopreserved and stored for use in a future cycle.

Frozen Embryo Transfer (FET)

Many reproductive techniques result in the development of more embryos than can be safely transferred in one treatment cycle. It is possible to freeze embryos and to thaw them at a later date for transfer to the patient. This has a slightly lower pregnancy rate than fresh embryo transfer (see Results) but negates the need for a woman to go through a full treatment cycle to have another chance of achieving a pregnancy. The embryos are transferred to the uterus without an anaesthetic in a hormonally controlled cycle. There has not been shown to be any increase in foetal abnormalities using frozen embryos. Embryos can be frozen up to 6 days after insemination. To be suitable for freezing, embryos must be growing at the expected rate and have few fragments between the cells of the embryos. If only one embryo is frozen from the original cycle, it is recommended that further IVF cycles are undertaken in order to have sufficient embryos for subsequent thawing and transfer.

If donor gametes are involved, embryos from different donors cannot be transferred together. It is important to be aware that approximately 75% of frozen embryos survive thawing in a condition which is suitable for transfer. This can be a very disappointing stage if you have had preparation for a frozen transfer cycle. The staff will be available to discuss this and support you and endeavour to provide the next step of your infertility care.

Long-term storage of frozen embryos is not recommended as a routine. The National Health and Medical Research Guideline recommend that embryos not be stored for longer than five years other than in specific circumstances.