State of the art in in-vitro oocyte maturation

The recovery of immature oocytes followed by in-vitro maturation (IVM) and in-vitro fertilization is an attractive alternative to conventional in-vitro fertilization treatment in which controlled ovarian stimulation with gonadotropins is used to increase the number of available oocytes and embryos. Significant progress has been made to improve pregnancy and implantation rates from in-vitro matured oocytes. This review summarizes current knowledge and achievements in human oocyte in-vitro maturation for clinical application, and will highlight recent advances reported in in-vitro maturation treatment.

It has been demonstrated that priming of ovarian immature oocytes with follicle-stimulating hormone or human chorionic gonadotropin prior to immature oocyte retrieval improves oocyte maturation rates and embryo quality as well as pregnancy rates in infertile women with polycystic ovaries or polycystic ovary syndrome. The size of follicles may be important for the subsequent embryonic development, but the developmental competence of oocytes derived from the small antral follicles is not adversely affected by the presence of a dominant follicle. However oocyte maturation in vitro is profoundly affected by culture conditions. Currently more than 300 healthy infants have been born following immature oocyte retrieval and in-vitro maturation. In general, the clinical pregnancy and implantation rates have reached 30-35% and 10-15% respectively in infertile women with polycystic ovaries or polycystic ovary syndrome.

In-vitro maturation treatment can now be offered as a successful option to infertile women with polycystic ovaries or polycystic ovary syndrome. It is possible to combine natural cycle in-vitro fertilization with immature oocyte retrieval followed by in-vitro maturation, and thus offer women with various causes of infertility reasonable pregnancy and implantation rates without recourse to ovarian stimulation. Further research remains to be done to address the mechanism of oocyte maturation in order to refine culture conditions and improve the implantation rate of oocytes matured in vitro.