Can Oocyte Diameter Predict Embryo Quality?

With the recent increased utilization of oocyte vitrification for the purpose of fertility preservation, information regarding the future fertility potential of the frozen oocytes is mandatory. Nowadays, there is a relative lack of data about prediction of assisted reproductive technique (ART) success relying on the retrieved oocytes. In the present study, we therefore aimed to investigate whether oocyte diameter might predict the quality of the developing embryo. A retrospective, single-center cohort study. Oocytes retrieved following controlled ovarian hyperstimulation cycles during 2016 and incubated in a time-lapse incubator system were analyzed. Oocytes were grouped by mean oocyte diameter (MOD) and incubated for 5 days before the final morphological evaluation done by an expert embryologist. A total of 471 cycles which yielded 3355 metaphase II oocytes were included in the analysis. Embryos developed from oocytes with MOD close to the average (Average 1SD < MOD < Average + 1SD) had increased good-quality blastulation rates compared with embryos that developed from very small or very large oocytes. Oocytes with MOD between 105.96 and 118.69 μm have better probability of becoming top-quality D5 blastocysts (17.1-17.4% grade 1 embryos). There is a correlation between oocyte's MOD and the embryo quality at day 5. The oocytes with near average MOD have a better chance to develop to a good-quality embryo. Therefore, the study suggests that MOD might serve as a predictor for embryo grading at day 5.