Relationship of the human cumulus-free oocyte maturational profile with in vitro outcome parameters after intracytoplasmic sperm injection

Purpose:We investigated whether the human oocyte maturational profile at the removal of cumulus/corona cells affects the fertilization rate and subsequent embryo quality after intracytoplasmic sperm injection. Methods: A total of 1011 oocytes from 150 cycles was included in this retrospective analysis. Cumulus-free oocytes that were in prophase or metaphase I of meiosis at the removal of cumulus/corona cells were incubated in vitro until they reached metaphase II (in vitro-matured oocytes) and were then immediately injected with a single spermatozoa. Oocytes that were in metaphase II at the removal of cumulus/corona cells (MII oocytes) received sperm injection after 3-4 hr of preinjection incubation. Results: The fertilization rate of the MII oocytes was significantly higher than that of in vitro-matured oocytes (81 vs 62%; P < 0.001). The cleavage rates were similar in the two groups (MII oocytes, 94%; in vitro-matured oocytes, 91%). However; MII oocytes had significantly higher percentages of good-quality embryos (grade 1-3 embryos, 87 vs 58%, P < 0.001) and embryos with high cumulative embryo scores (score 10-32 embryos, 62 vs 33%, P < 0.001). The mean cumulative embryo score of MII oocytes after fertilization was also higher than that of in vitro-matured oocytes (12.1 +/- 3.8 vs 8.8 +/- 3.4; P = 0.014). Conclusions: MII oocytes that extruded the first polar body at the removal of cumulus/corona cells had better fertilization rates and embryo morphology than in vitro-matured oocytes that extruded the first polar body following the removal of cumulus/corona cells and in vitro culture.