Ultrastructural aspects of human immature oocytes

In vitro fertilization, one of assisted reproduction`s technique is, for some couples, the only possibility to conceive a child. One of the main condition that must be fulfield in order to reach this goal is the quality of human oocytes. The ovarian stimulation protocols used have as an important goal the oocytes quality. The maturity grade of the oocytes is a good indicator of their quality.The mature oocytes are prefered for fertilization, because the immature oocytes do not fertilize.The main objective of this study is to characterize the immature oocyte, in order to explain why they do not fertilize. For this study were used human oocytes obtained from the couples who underwent infertility treatment at „Bega” Universitary Clinic of Obstetric and Gynecology Timisoara, IVF Department. The results obtained revealed new aspects of zona pellucida`s ultrastructure.These aspects can explain why the immature oocytes do not fertilize, compared with the mature oocytes. The conclusion which can be drawn is that in order to increase the pregnancy rate for the infertile couples which undergo IVF, the stimulation has to be made in such way that the number of immature oocytes obtained to be minimum.