In-vitro oocyte maturation: some questions concerning the initiation and prevention of this process in humans.

Human oocytes isolated from healthy non-preovulatory antral follicles which had not been stimulated spontaneously resumed meiosis at a low rate (31%) when compared with those from atretic follicles (73%). Human follicular fluid did not inhibit spontaneous maturation of rat oocytes in vitro, regardless of the quality or maturity of the follicle or the treatment of the patient. In the human, oocyte maturation may involve a stimulatory process as well as a removal of inhibition.