To assess the maturational status of each female, fifteen oocytes
were randomly chosen among the most advanced mode of developing
oocytes on Wednesday and Thursday, or among the ovulated oocytes
(eggs) on Friday. The morphology of lipid droplets in each oocyte was
classified into ten stages according to Unuma et al. (2011a). Median
stage of the fifteen oocytes was defined as the stage for the individual.
Long and short diameters of each of the fifteen oocytes were measured
with digital calipers and averaged. The increasing rate in oocyte diameter
fromMIS injection to ovulationwas calculated for each female using
the following formula