Current status of the cryopreservation of human unfertilized oocytes

Cryopreservation facilitates the long-term storage of oocytes from patients in danger of losing ovarian function and allows greater flexibility in fer tility services for other patients. If some of the oocytes collected follow ing ovulation stimulation are stored prior to fertilization, this alleviate s many of the ethical concerns associated with embryo preservation. Concern s that cryopreservation could lead to disruption of the spindle and chromos omes, thus leading to genetic abnormalities of the offspring produced, mean that this procedure is not permitted in some countries. The recent spate o f human live births from thawed oocytes has prompted the granting of the fi rst licence allowing the use of thawed oocytes in the UK, However, the succ ess rate of this procedure is still low and further research is required to refine these techniques and to develop new ones.