Intracytoplasmic sperm injection: correlation of oocyte grade based on polar body, perivitelline space and cytoplasmic inclusions with fertilization rate and embryo quality

The extent to which the morphology of the oocyte at the light microscopy level is related to the results of intracytoplasmic sperm injection (ICSI) is controversial. In this study, after cumulus removal, oocytes were graded into four groups according to the status of the first polar body, size of the perivitelline space and the presence of cytoplasmic inclusions. Oocyte data from 65 consecutive patients were reviewed. The results showed that, for oocytes without cytoplasmic inclusions, the fertilization rate and embryo development beyond 2-cell stage were significantly lower (P < 0.01) in the oocytes at grade 1-2 (poor) than those in oocytes at grade 3-4 (good). Grade 4 oocytes without inclusions gave the highest proportion (66.7%) of good embryos with grading 1-2 (grade 1 best; P < 0.01). A higher proportion of grade 1-2 oocytes (44.7%; P < 0.05) was obtained from patients older than 35 years. More oocytes containing cytoplasmic inclusions were seen in patients diagnosed as having female factor infertility (24.9%; P < 0.01) and older than 35 years (26.5%; P < 0.05) compared to patients with male factor infertility and younger than 35 years. The fertilization rate and embryo development were not associated with the oestradiol concentration on the day of human chorionic gonadotrophin administration or the total number of oocytes retrieved. The results suggest that human oocyte grading based on the triple factors first polar body, size of perivitelline space and cytoplasmic inclusions is related significantly to fertilization rate and embryo quality after ICSI.