Ovarian and oocyte cryopreservation

The present article is an update on progress in the two available techniques of oocyte and ovarian cryopreservation: slow cooling/rapid thawing and vitrification. A new line of research has opened in recent years: freezing the whole ovary with its vascular pedicle, so as to enable vascular grafts limiting ischemia-related follicle reserve loss.

The technique of mature oocyte vitrification has advanced significantly, with improved oocyte physiology, increased safety, and higher clinical pregnancy rates. The number of studies on whole ovary freezing has grown, and there has been a large-mammal (sheep) live birth by orthotopic graft with vascular anastomosis of a cryopreserved ovary.

Ovarian and oocyte cryopreservation is essential to conserving the fertility of young women. Results of mature oocyte freezing techniques have improved significantly over the past few years, but remain poorer than those with embryo freezing. Mature oocyte vitrification is progressing well, but requires safety validation in view of the high cryoprotectant concentrations used. Ovarian cortex fragment freezing is widely used in patients, with two live births after orthotopic graft, worldwide. The problem of rapid graft exhaustion has led to a focus on whole ovary cryopreservation which has resulted in one live birth in a ewe.