Clinical utility of early rescue icsi

Abstract

Rescue ICSI (r-ICSI) for 1-day-old oocytes is associated with poor developmental potential for embryos due to oocyte aging in vitro. Early r-ICSI has accordingly been proposed as a treatment modality, and is reported to have some utility. In an early r-ICSI protocol, oocytes are checked for extrusion of 2PB as a predictor of fertilization after short insemination, and oocytes with predicted non-fertilization are then subjected to ICSI on the same day. At our clinic, after the 5-h initial insemination, oocytes are examined for extrusion of 2PB. They are then reexamined around the 7 or 8-h timepoint, and the final 2PB extrusion rate is calculated. r-ICSI is promptly performed in cases where this rate does not exceed 50% to prevent poor fertilization or total fertilization failure. In this study, we calculated the differences in embryo utilization rate, and the pregnancy rate achieved after frozen-thawed ET(FTET) to investigate the clinical utility of early r-ICSI in cases where it was indicated. Retrospective date analysis Early r-ICSI was indicated in 161 cycles in cases undergoing c-IVF between 2015 and 2016. We calculated the following parameters after early r-ICSI for the indicated cases: 2PN rate, multiple PN rate, blastocyst rate. We also compared the pregnancy rate after FTET of early r-ICSI-derived blastocyst (mean age 36.4±4.2 and 36.9±4.0 years at cryopreservation and ET, respectively) with that after FTET of normal ICSI(n-ICSI)-derived blastocyst (mean age 37.4±3.8 and 38.0±3.9 years at cryopreservation and ET, respectively). A total of 916 MII oocytes were retrieved in the 161 c-IVF cycles, and 537 of these oocytes were subjected to early r-ICSI after determination of the 1PB following a 7- to 8-h initial insemination. The results obtained after early r-ICSI were as follows: 2PN rate of 380/547 (70.8%), multiple PN rate of 84/537 (15.6%), blastocyst rate of 184/331 (55.6%). The pregnancy rate of FTET with early r-ICSI-derived blastocyst was 23/43 (53.5%), and that with n-ICSI-derived blastocyst was 494/1298 (38.1%). No significant difference was noted between the two pregnancy rates and their backgrounds. We found that 24% of oocytes with predicted fertilization (based on 2PB extrusion) on the day of insemination were unfertilized. The post-early r-ICSI multiple PN rate was high. Increased accuracy is needed for prediction of fertilization based on the 2PB. However, even with the current level of accuracy, early r-ICSI yielded increases in parameters relative to non-treatment as follows: the number of fertilized oocytes acquired was 637 versus 257 (247.9%), the number of blastocysts acquired was 320 versus 136 (235.3%). Early r-ICSI clearly contributes to increased embryo utilization rate. The pregnancy rate obtained with early r-ICSI after FTET was similar to that for n-ICSI-derived blastocysts. Based on the above results, early r-ICSI exhibited marked clinical utility.