Early oocyte denudation does not compromise ICSI cycle outcome: a large retrospective cohort study

This retrospective cohort study of 2051 consecutive fresh non-donor intracytoplasmic sperm injection (ICSI) cycles investigated whether time from oocyte retrieval to denudation, precisely measured and recorded by an operator-independent automated radiofrequency-based system, affected cycle outcome. ICSI cycles were divided into two groups: group I (denudation within <2 h of oocyte retrieval, n = 1118) and group II (denudation 2-5 h after oocyte retrieval, n = 933). Univariate analysis by two-sample t-test or Mann-Whitney test was used, as appropriate. Both groups were comparable with regards to mean number of oocytes retrieved and fertilized normally after ICSI. The mean number of embryos transferred and surplus embryos cryopreserved at the blastocyst stage were similar. There was no significant difference in fertilization, embryo implantation, pregnancy, clinical pregnancy or live birth rates between the groups. Analysis of group I ICSI outcome after subdivision into immediate (up to 30 min) and early (31-119 min) denudation showed no statistically significant differences between the two subgroups. In conclusion, early oocyte denudation within <2 h after retrieval does not appear to compromise ICSI cycle outcome, permitting more efficiency and flexibility in scheduling laboratory workload. As this was a retrospective observational study, further prospective studies are required to confirm the findings.