The Effect of Delayed Maturation in Oocytes After Retrieval on Embryo Potential and Ploidy Status

Presented at: ASRM 2022, Anaheim, CA

Authors: Jennifer Matucha, M.S., Bradford Bopp, M.D., Matthew Will, M.D., Erica Anspach Will, M.D., Kate O’Leary, M.D., Glen Adaniya, Ph.D.

Objective: The objective was to determine if the delayed maturation of oocytes affected subsequent embryo development, as well as the impact of these oocytes within in vitro fertilization (IVF) cycles with preimplantation genetic testing for aneuploidy (PGT-A).

Materials and Methods: This exempt retrospective chart review was approved by the Ovation Research Ethics Committee. Cycle data was collected for 422 IVF with PGT-A cycles, using intracytoplasmic sperm injection (ICSI) as the method of insemination, between January 2021 and January 2022. Retrievals were performed 36 hours post-trigger. Maturity was initially assessed after cumulus cell removal, and oocytes reassessed at the time of ICSI were labeled Metaphase I with delayed maturation to Metaphase II (MI; N = 189), or mature Metaphase II oocytes at the time of denuding (MII; N = 1,512). Cycles had at least one oocyte with delayed oocyte nuclear maturation (Delayed; N = 130) or no delay in maturation (No Delay: N = 292). There were 1,953 embryos biopsied, and samples were sent to a single testing facility for PGT-A. Delayed cycles were examined to compare fertilization and embryo development between MI and MII sibling oocytes. Primary outcomes reviewed were fertilization and embryo development, as well as rates of euploidy, aneuploidy and mosaicism. Independent t-tests were used to compare data such as age, anti-mullerian hormone (AMH), body mass index (BMI), and number of oocytes retrieved. Aggregate data was analyzed by proportional z-tests, and a p-value < 0.05 was defined as statistically significant, with a 95% confidence interval.

Results: The time between retrieval and initial maturation assessment, time between initial assessment and ICSI, average age, and BMI were not significant between Delayed and No Delay cycles. A significant difference was seen between AMH (3.4 ± 2.9 vs. 2.8 ± 2.3; p=.018) and the average number of oocytes retrieved (16.1 ± 9.0 vs. 13.2 ± 9.0; p=.002). Within the Delayed cycles, matured MI oocytes had significantly lower fertilization (59% vs. 77%, p<0.001), day 3 progression (67% vs. 83%, p<0.001), and blastocyst development (21% vs 55%, p<0.001) compared to their sibling MII oocytes. Delayed cycles had a significantly lower fertilization rate compared to No Delay cycles (75% vs. 82%; p<0.001). Significantly higher post-ICSI atretic rates (6% vs 4%, p=.027) were also found in Delayed cycles, but total maturation; blastocyst development; and rates of euploidy, aneuploidy and mosaicism did not differ between the two groups.

Conclusions: Oocytes with delayed maturation have significantly lower fertilization and blastocyst development compared to their sibling oocytes. The cycles with these oocytes were affected by having increased post-ICSI atretic rates and lower fertilization, but both groups resulted in similar blastocyst development and euploidy.

Impact Statement: Although oocytes with delayed maturation have decreased embryo potential, some of these oocytes go on to create euploid blastocysts. Ultimately, it is beneficial to the patient to reevaluate oocyte maturation at ICSI to increase the number of embryos for transfer.