P–169 Does increasing the time interval between Oocyte-Retrieval and Oocyte-Denudation improve the results in ICSI cycles ?
Authors: Singh M , Singh R 
Published: August 2021

Abstract

Study question
What should be the optimal time interval which elapses between oocyte retrieval and denudation followed by ICSI , for optimal results in ART cycles ?

Summary answer
Our study suggests that an optimum interval between oocyte retrieval and oocyte denudation followed by ICSI, leads to better results in ART cycles.

What is known already
It is widely accepted that the best timing for OPU is 34–39 hours after ovulation trigger. Some studies suggest that preincubation time before ICSI can be beneficial when it comes to fertilization and pregnancy rates while late ICSI (fertilization) may have negative results due to oocyte ageing. Other studies claim that there is no significant difference in ART results when ICSI is performed between 2–6 hours post Oocyte-Retrieval (OR) . Few studies state that 1–3 hours of COC-culture prior to denudation and oocyte injection is better as far as fertilization , embryo quality and improved oocyte cytoplasmic maturity is concerned.

Study design, size, duration
RCT of 234 ICSI cycles was carried out between 2017–2019. Patients were divided into two groups-: A- Early denudation with ICSI and B- Late denudation with ICSI.Both the groups were comparable in terms of female age, number of oocytes, day of transfer, number of embryos transferred and embryo quality. Fresh or frozen embryos were transferred , which were always derived from the same stimulation cycle. Exclusion criteria were : Severe male factor / TESA / PESA.

Participants/materials, setting, methods
234 ICSI cycles with similar ovarian stimulation protocols were analyzed as per time range between triggering, OPU, denudation and ICSI. Patients were divided into two groups: A- Early denudation (1–2 hours after OPU) with ICSI (1–2 hours after denudation) and B- Late denudation (4–6 hours after Oocyte-Retrieval ) with ICSI (1–2 hours after denudation).Primary outcomes were oocyte maturation and fertilization rates and secondary outcomes were clinical pregnancy rate and abortion rates.

Main results and the role of chance
In group B ( Late denudation and ICSI), the mean fertilization rate was 67% and the Clinical Pregnancy rate was 46%. This was better than the mean fertilization rate of 56% and clinical pregnancy rate of 39% observed in group A ( Early denudation and ICSI). However the difference was not statistically significant. Therefore, ideal maturation rates were observed when denudation ( followed by ICSI ) was delayed and done 4–6 hours after Oocyte-Retrieval. In ICSI cycles in ART , ovarian stimulation is used to induce the simultaneous growth of multiple follicles, followed by final maturation and ovulation triggering with exogenous hCG. or GnRH-Agonist or both. Generally, oocyte retrieval (OR) is performed 34 - 36h later. In addition, 2–4 hours in culture of the cumulus oocyte complexes (COC) prior to oocyte injection is believed beneficial for fertilization and embryo quality, probably due to improved oocyte cytoplasmic maturity. However, in large ART centers with high workloads, following such definite time intervals is frequently very difficult.

Limitations, reasons for caution
In large busy centers , maintaining meticulous time intervals is difficult . As our study numbers are small, larger multicentric trials are required in order to confirm our findings and to provide more robust data . This data cannot be applied to IVM, TESE / PESE and severe male-factor infertility.
Wider implications of the findings: To achieve a successful fertilization, both nuclear and cytoplasmic maturity are required. Our Study indicates that a slight delay in denudation following Oocyte-Retrieval , will yield a higher number of good quality oocytes. A higher success rate can also be expected due to more number of embryos available for transfer.

Trial registration number
Not applicable