Cryopreservation of Unfertilized and Pronuclear Human Oocytes

Journal für Reproduktionsmedizin und Endokrinologie - Journal of Reproductive Medicine and Endocrinology 2007; 4 (2): 92-93

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Keywords: Kryopreservation,  Oozyte,  Pronukleus,  Reproduktionsmedizin,  cryopreservation,  oocyte,  pronuclear stage

Unlike the cryopreservation of male gametes, cryopreserved female gametes have found little entry into clinical reproductive practice. Although potential applications in the preservation of fertility and treatment of infertility are numerous, the efficacy of the oocyte freezing process is still low due to specific properties of mature oocytes. The freezing of earlier stages has been hampered in the past by difficulties in the in vitro maturation of germinal vesicle oocytes. In contrast, cryopreservation of fertilized oocytes at the pronuclear stage and of embryos has become a routine procedure in human assisted reproduction. The use of controlled ovarian stimulation protocols initiates the maturation of large numbers of oocytes, of whom more may become fertilized than medically reasonable and/or legally permitted to be transferred into the uterine cavity for implantation. In case of surplus fertilization, cryopreservation provides a means of achieving pregnancies beyond the initial cycle (using fresh embryos) without recurring to another oocyte retrieval.