Failure of meiotic competence in human oocytes.

The administration of hCG to women undergoing in vitro fertilization and embryo transfer (IVF/ET) results in the meiotic maturation of cumulus-oocyte complexes (COC). Sometimes oocytes being aspirated for lVF/ET fail to resume meiosis in vivo and even after a subsequent 20-h incubation in vitro and are thus defined as meiotic competence failure (MCF) oocytes. The relationship between the proportion of MCF oocytes and other IVF/ET outcomes was studied over 3 years in 703 tested cycles of 487 women. Women yielding one or more MCF oocytes in at least one menstrual cycle represented 8.6% of this population and were defined as MCF women. Cumulus state in the MCF oocyte population was characterized as mature in 57.4 ± 6.7%, intermediate in 13.9 ± 4.0%, immature in 24.1 ± 8.7%, and atretic in 4.6 ± 2.7%. These values differed significantly, by 0.6-, 2.9-, 7.1-, and 4.6-fold, respectively, as compared to the corresponding COC aspirated from women yielding only meiotically competent (MC) oocytes. In a menstrual cycle yielding both MC and MCF oocytes, the IVF/ET variables were evaluated in the MC oocytes. Thus, in such cases the incidence of fertilization or cleavage and the number of blastomeres per embryo were significantly reduced concomitant with the increase in percentage of MCF oocytes. When the percentage of MCF oocytes was 25% or more, no pregnancy was achieved. Various follicular parameters and serum 17p-estradiol (E,) and progesterone (P4) levels were compared in MC and MCF women over the four days preceding day of aspiration. In women yielding 25% or more MCF oocytes, the normal increase in follicular number was attenuated, and the serum E,/ number of follicles remained significantly high on day of aspiration, as compared to the corresponding values in women yielding only MC oocytes. This study suggests that the increase in percentage of MCF oocytes represents an overall decrease in IVF/ET variables in terms of oocyte and follicular functionality.