Dados do Trabalho

Title

Immediate oocyte denudation or after two hours of cumulus-oocyte complexes in vitro culture: does it really matter?

Objective

The intense cell communication that occurs in cumulus-oocyte complexes (COCs) is limited after ovulation trigger and at time of ovum-pick-up (OPU). However, it is still uncertain if the remained communication, such as through paracrine molecules, is important during this period until in vitro fertilization. For the ICSI procedure, oocyte denudation could be performed immediately after OPU or after 2-3 hour of in vitro culture of the COCs, but there is no consensus about the optimal denudation time. The aim of this study was analyze the effect of the time until oocyte denudation on fertilization and cleavage rates.

Methods

In this retrospective cohort study, 631 ICSI cycles between 2018 and 2023 were split into two groups; 281 cycles in which denudation was performed immediately after OPU (IM group) and 350 cycles with denudation after 2 hours of COCs in vitro culture (2h group). The excluding criteria were male factor, receptors and cryopreserved sperm cycles. In IM group the ICSI was performed 2 hours after OPU, and in 2h group 3 hours after. The fertilization was checked on day 1 and the cleavage stage of embryos was assessed on day 2 and 3. The age of both groups was compared, but for better understanding of denudation time influence, cycles were also separated by maternal age (< 31 years old, 31-34 years old, 35-37 years old, 38-39 years old, 40-42 years old and > 42 years old). The fertilization (2PN embryos / injected oocytes) and cleavage rates (cleavage embryo / 2PN embryos) between both groups, as well as data from age related subgroups, were compared using Chi square and Fisher’s exact tests with p value ≤ 0.05 considered significant.

Results

Although fertilization rate was higher in 2h group (79.53%; 2,051/2,579) when compared to IM group (74.46%; 1,478/1,985), cleavage rate was improved in IM group (IM group; 96.48% (1426/1478) and 2h group; 77.18% (1583/2051)). The subgroup analysis showed that only cycles with maternal age in the ranges 31-34 and 35-37 years old presented an increase in fertilization rate in the 2h group (80.49%; 590/733 and 81.78%; 552/675, respectively) comparing to cycles with immediate denudation (78.48%; 175/223 and 70.77%; 368/520). Interestingly, among all subgroups, the cleavage rate was increased in IM groups (< 31 years old; 98.86% (173/175), 31-34 years old; 95.39% (414/434), 35-37 years old; 98.64% (363/368), 38-39 years old; 96.32% (183/190), 40-42 years old 92.77% (231/249) and > 42 years old; 100% (62/62)) when compared to 2h groups (< 31 years old; 75.98% (174/229), 31-34 years old; 79.83% (471/590) , 35-37 years old; 68.30% (377/552), 38-39 years old; 85.97% (288/335), 40-42 years old; 79.30% (226/285) and > 42 years old; 78.33% (47/60)).

Conclusion

Overall, our data suggest that immediate oocyte denudation after OPU, and consequently shorter the time between oocyte recovered and ICSI process, improves cleavage rate, independently of maternal age.

Keywords

denudation time, fertilization rate, cleavage rate