Effect of cumulus cell removal 4 h post-insemination on fertilization and embryo quality: a prospective randomized sibling-oocyte study.

PurposeThe study was designed to evaluate whether cumulus cell removal 4 h post-insemination could influence fertilization and embryo quality.MethodsThe study included 61couples undergoing standard long down regulation protocol from July 2011 to May 2012. Sibling oocytes of each patient were randomly assigned to either the 4 h group or the 20 group. For the 4 h group, cumulus cells were removed 4 h after gamete coincubation; for the 20 group, cumulus cells removal was performed 20 h after insemination. Fertilization rate, embryo quality, pregnancy rate and implantation rate were assessed.ResultsA total of 801 sibling cumulus-oocyte complexes (COCs) were randomized to the 4 h group (421 COCs) or 20 h group (380 COCs). There was no difference in the two pronuclei, one pronucleus and grade 1-2 embryo rate. Three pronuclei rate was significantly higher in the 4 h group compared to the 20 h group (12.6 % vs. 8.2 %, P = 0.041). Comparison of embryo transfer cycles in which either embryos from the 4 h group or 20 h group were transferred did not reveal any statistically significant differences in pregnancy or implantation rates.ConclusionThe results of the present study indicate that cumulus cell removal 4 h post-insemination may increase the percentage of tripronuclear zygotes. However, normal fertilization rate, embryo development, clinical pregnancy rate and implantation rates are not influenced by the timing of cumulus cell removal.