Strategies in human in-vitro maturation and their clinical outcome.

The basis of in-vitro maturation (IVM) is the maturing in vitro of oocytes from the germinal vesicle (GV) stage of development to the metaphase II stage. Experience in handling immature oocytes has been obtained from two main groups. The first group is women suffering from polycystic ovarian syndrome, who are extremely sensitive to stimulation with exogenous gonadotrophins in assisted reproduction, and have a significant risk of developing ovarian hyperstimulation syndrome (OHSS). The second group is regular cycling women with normal ovaries referred for IVF due to severe male infertility. In both groups, aspiration of immature oocytes has been performed in unstimulated cycles and after priming with human chorionic gonadotrophin or FSH respectively. Clinical pregnancy rates of 24% per aspiration have been obtained. Children born after IVM appear to be healthy. These data, taken together, suggest that in future, immature oocyte retrieval combined with IVM could replace conventional IVF in selected patients.