Background: Optimal embryonic developmental competence depends on proper oocyte maturation. Nuclear maturation is usually achieved in vivo and can be assessed by the time of ovum pickup; however, cytoplasmic maturation cannot be readily assessed and might be incomplete. Cumulus cells surrounding the oocyte might play a role in the oocyte cytoplasmic maturation.
Objective: To investigate the effect of denudation timing after one and 2 hours on the laboratory and reproductive results in ICSI cycles.
Materials and Methods: In a randomized study including 160 ICSI cycles, 2621 oocytes were randomized into two groups according to denudation timing after 1 or 2 hours of OPU. MII injection was performed immediately. Each patient had 1-2 fresh embryo transfer at day 5.
Results: There is no significant difference in maturation rate between groups I and II. The total fertilization rate between the two groups was comparable at 72.6% & 73.4%, respectively (p=.675). In contrast, the cleaved embryos/ diploid zygotes in group I (94.7%) were significantly lower than those in group II (99.1%, p<.001). Also, cleaved embryos/MIl was 68.7% in group I and 72.7% in group II (p=.045). Both groups had no significant difference in the quality of embryos on days 2, 3, and 5. The available blastocysts on day 5 and the transferred grade I blastocysts were comparable. The clinically pregnant females and implantation rates were not significantly different between both groups.
Conclusions: Oocyte-cumulus cell contact is important for cytoplasmic maturity. Although the impact of a higher cleavage rate after 2 hours of preincubation does not affect the clinical pregnancy rate in the fresh cycles, it may increase the probability of achieving a live birth after utilizing all cryopreserved embryos.