In vitro maturation of human immature oocytes for fertility preservation.

Cryopreservation of embryos, oocytes, or ovarian tissues is the main option for female fertility preservation. Oocyte cryopreservation has emerged as especially important: the dramatic increase in the number of infants born from vitrified oocytes indicates that it is becoming one of the most important intervention options. However, oocyte cryopreservation with standard controlled ovarian hyperstimulation may not be feasible for some cancer patients as there are serious concerns about the effect of ovarian stimulation with hormones on the risk of cancer recurrence. Also, urgent gonadotoxic cancer treatment may not allow sufficient time for a patient to undergo hormonal ovarian stimulation. Thus, immature oocyte retrieval from ovaries without ovarian stimulation followed by in vitro maturation and vitrification is a promising fertility preservation option for women who cannot undergo ovarian stimulation or cannot delay their gonadotoxic cancer treatment. Immature oocytes can be collected from the ovaries during both the follicular and luteal phases, which maximizes the possibility for fertility preservation. The combination of ovarian tissue cryopreservation with immature oocyte collection from the tissue followed by oocyte vitrification via in vitro maturation represents another promising approach of fertility preservation in young women with cancer.