Cryopreservation is the freezing and thawing of embryos for use in future in vitro fertilization (IVF) cycles.

During an IVF cycle, the fertilized eggs are transferred to incubators where they develop until ready for transfer to the uterus, usually 3-5 days.

The number of mature embryos available for transfer varies by patient, as does the number placed back in the uterus. Since the maximum number of embryos that will be transferred to the uterus is limited, there are often excess embryos.

Embryologists have perfected techniques for transferring embryos to different solutions as they are frozen and thawed. Great care is taken not to rupture the membrane surrounding the embryo.

The major advantages to using frozen embryos in future IVF cycles is that the female does not have to undergo ovulation induction, which also dramatically reduces medication cost. Success rates are variable depending on patient characteristics, embryo quality and clinical history.