Role of oocyte morphology on fertilization and embryo formation in assisted reproductive techniques

Objective: To assess the influence of MII oocyte morphology on the fertilization outcome and embryo development in ART cycles. Since, age may affect the quality of oocyte, the role of women's age was also evaluated following IVF or ICSI cycles. Materials and Methods: 200 MII oocytes from 30 IVF and ICSI cycles were evaluated. The morphology of oocytes that were fertilized in IVF cycles (IVF+) was compared with failed fertilization (IVF-). The oocytes were similarly categorized in the ICSI procedure (ICSI+ and ICSI-). The criteria for morphological evaluations were: a. normal oocytes showed clear cytoplasm with homogenous fine granularity; b. granular oocytes, dark with granularity either homogenous in whole cytoplasm or concentrated in the central portion of the oocyte; c. cytoplasmic inclusions comprised vacuoles presumed to be of endocytotic origin; d. dark zona pellucida (ZP), e. fragmented polar body (PB) of different sizes; f. non-spherical shape of oocyte; and g. wide previtelline space (PVS). Embryo transfer took place 48 h after insemination/ injection. The statistical significance of the data was analyzed using chi-square and Fisher's exact tests. Results: A total of 67 and 78 oocytes were fertilized in IVF and ICSI cycles, respectively. 46.3% and 35.9% of fertilized oocytes were shown with normal morphology in IVF and ICSI cases, respectively. The rates of grade A & B embryos were significantly higher in oocytes with normal morphology (P<0.05). The mean number of embryos transferred was similar in IVF and ICSI groups (3.3±0.4 versus 3.0±0.9). In IVF+ and ICSI+, fragmented PBs were the highest rates of single abnormality with 11.9% and 14.1%, respectively. Also, multiple abnormalities were observed in 21.0% and 48.5% of oocytes in IVF+ and IVF-, respectively (P<0.001). 15.4% and 31.8% of the oocytes from ICSI+ and ICSIwere presented with more than one abnormality. Refractile bodies were the highest type of single abnormality (18.2%) in ICSIgroup. Conclusions: In both IVF and ICSI, the highest rates of fertilization and embryo formation took place in oocytes with normal morphological features that were retrieved from young patients. The most single morphological features involved in failed fertilization were refractile body in ICSI and ooplasm granulation in IVF cases. The data suggest that oocyte quality plays a major role in fertilization process and embryo development in ART program.