Binovular human ovarian follicles associated with in vitro fertilization: incidence and outcome.

Binovular follicles were found in 15 (0.3%) of 4,695 follicles containing oocytes. These binovular follicles were either with adjacent cumulus complexes (9 cases), or separate corona radiata and common cumulus mass (1 case), or two oocytes within a single zona pellucida (5 cases). In each of the latter form, there was a smaller and a larger oocyte. All the smaller oocytes and two larger ones possessed a germinal vesicle, whereas the remaining three larger oocytes were mature and developed normally. Though being exposed to the same intrafollicular milieu, there can be a difference in the maturity of the nucleus and characteristics of the cytoplasm of both oocytes.