P-255 Increased time in thawing solution improves human oocyte warming outcomes

Abstract

Abstract Study question Can increased time in thaw solution improve oocyte survival and outcomes following vitrification/warming? Summary answer Exposing vitrified oocytes to the first step thawing solution for 90 seconds improved oocyte survival compared to 60 second exposure. What is known already Oocytes are a sensitive cell type and careful handling of the cells is required to obtain high outcomes following vitrification and warming. Carefully timed exposure to various vitrification solutions is required to avoid toxicity and ensure proper vitification. Similarly, proper and carefully timed exposure to warming solutions is required to avoid oocyte damage upon warming. Recent reports suggest a modified and rapid warming protocol may be beneficial for vitrified blastocysts. However, oocytes are unique cells and may require unique considerations to optimize warming. Study design, size, duration Retrospective analysis of donor oocyte warming outcome data within a single IVF lab over a 12 month period comparing a 60 second first step during oocyte warming (control n = 637 oocytes) versus a very consistent 90 second exposure (n = 672 oocytes) to the first step thawing solution. Participants/materials, setting, methods Human donor oocytes were vitrified using the standard Kitazato protocol with ES drop merging and loading on CryoTop devices using the wicking method prior to plunging into liquid nitrogen. Warming was performed using the standard protocol of 60 seconds in thaw solution (TS) or 90 seconds exposure. All cycles utilized ICSI and excluded testicular sperm samples. Survival, fertilization and blastocyst development were compared between the two exposure groups. Data were analyzed utilizing Fisher’s Exact Test. Main results and the role of chance Oocyte survival differed between the two timing treatments, with exposure to TS for 90 seconds yielding higher oocyte survival (96.1%) than 60 secondsTS exposure (92.0%), p < 0.002. No differences in fertilization following ICSI (78.3.0% vs. 79.0%) orin good quality blastocyst conversion (≥3BB) on day 5 (22.1% vs. 25.1%) or by day 7 (55.3% vs. 55.7%) were apparent. The aneuploidy rate of blastocysts were similar, with 28.5% in the 90 second TS treatment group and 27.3% in the 60 second TS exposure group. Limitations, reasons for caution Data were examined retrospectively and sibling oocyte splits were not utilized. Clinical outcomes following resulting embryo transfer were not examined. Wider implications of the findings These data may help improve oocyte warming protocols and resulting outcomes. Trial registration number not applicable