The timing of cumulus cell removal for intracytoplasmic sperm injection influences the capability of embryonic development

PURPOSE: To determine whether the presence of intact cumulus cells during the preincubation period for ICSI should be considered as a critical factor in fertilization and embryonic development. METHODS: The cohort of this prospective randomized study was limited to infertile women younger than 39 years of age who underwent controlled ovarian stimulation for ICSI between October 2013 and May 2015 and whose embryos were to be incubated until day 5. Women with estradiol levels of <2000 pmol/L on the day of HCG injection were excluded. Cumulus cells were removed immediately after OPU in Group A and at 120 minutes after OPU in Group B. ICSI was performed with all mature oocytes, and fertilized oocytes were cultured to the blastocyst stage. Maturation, fertilization, blastocyst, good quality blastocyst, pregnancy, live birth, and miscarriage rates were compared. RESULTS: There were no significant differences in maturation, fertilization, blastocyst, pregnancy, live birth, or miscarriage rates between Groups A and B. However, the percentage of good quality blastocysts was significantly higher in Group B than Group A (52.0% vs 33.1%). CONCLUSIONS: Intact cumulus cells should be maintained during the preincubation period, as they are important to embryonic development after fertilization.