Embryological aspects of oocyte in vitro maturation.

In Vitro Maturation (IVM) is a method that immature oocytes in antral follicles are extracted and matured in laboratry conditions. This review has attempted to provide the current knowledge and recent findings in in vitro maturation of oocytes and highlights the most important factors involved in this process. The review is based on literature reports and the author's experience. In IVM cycles, the time of administration of hCG is depending on the diameter of the largest follicle that has been determined to be about 10-12 mm to prevent the detrimental effect of dominant follicle (DF). Higher number of in vivo matured oocytes with dispersed cumulus cells (CC) pattern can be achieved by increasing the time of hCG injection up to 38 h. Growing of oocytes during the final hours of in vitro maturation has profound effect on the following outcome. Injection of IVM oocytes must be delayed at least 1 h after extrusion of the first polar body. IVM outcome shows that the pregnancy rate is low in pure immature oocytes except PCO(s) (Polycystic ovaries and Polycystic ovarian syndrome) cases. Furthermore, endometrial quality may have a crucial role in this respect after non hCG-triggered IVM. The formulation of different types of maturation media shows that they are generally supplemented with recombinant FSH and hCG. Taurine and calcium as unique components of blastocyst medium have been supposed to be valuable to IVM media. Pyruvate and adenosine triphosphate (ATP) and Epidermal Growth Factor (EGF) have been proposed as additives for maturation media. IVM is not a suitable treatment for women over 40 years. Different categories of patients could be candidate for IVM. Despite of old concept in low outcome and caution in IVM indications, innovative findings in this field have opened new windows in the treatment of patients.