Morphology of in-vitro matured oocytes: impact on fertility potential and embryo quality

BACKGROUND: The purpose of the present study was to investigate the morphology of in-vitro matured metaphase II (MII) oocytes and to observe if there was a difference in the morphology between polycystic and normal ovaries. Furthermore, the morphology of in-vitro matured MII oocytes was related to their subsequent fertilization and cleavage rates and to embryo quality. METHODS: This retrospective study included 264 MII oocytes obtained in 100 consecutive cycles. Oocyte retrieval was performed transvaginally and cumulus enclosed oocytes were matured for 28-30 h before evaluation. Prior to ICSI, all MII oocytes were graded into three groups according to the number of anomalies: grade I: oocytes without any anomaly (n = 144, 54%), grade II: oocytes with one anomaly (n = 87, 33%) and grade III: oocytes with at least two anomalies (n = 33, 12.5%). RESULTS: Oocyte grades did not differ between women with polycystic ovaries [grades I, II and III respectively: 58/94 (61.7%), 29/94 (30.9%) and 7/94 (7.4%)] and women with normal ovaries [grades I, II and III respectively: 86/170 (50.6%); 58/170 (34%); 26/170 (15.3%)]. Morphology was not related to fertilization rates. The cleavage rate was, however, affected by morphological anomalies (grade I [77/144 (53.5%) versus grade II 33/87 (37.9%) (P = 0.03)], although no significant decrease in cleavage rate could be demonstrated when all grade II and III oocytes were compared with normal oocytes. Significantly more embryos of good quality developed after grade I oocytes [54/144 (37.5%)] compared with those from grade II and grade III oocytes (22/120; P = 0.001). The presence of cytoplasmic abnormalities significantly decreased the cleavage rate (P = 0.04) and also the number of good quality embryos (P < 0.001). CONCLUSION: The in-vitro maturation of oocytes without anomalies yields higher quality embryos, with higher cleavage rates, than those with anomalies.