P-247 Total Fertilization Failure after conventional IVF: it is not the end of the story

Abstract Study question Could Rescue IntraCytoplasmatic Sperm Injection (R-ICSI) coupled with frozen transfers be an effective treatment for Total Fertilization Failure (TFF) after conventional InVitro Fertilization (c-IVF) cycles? Summary answer Applying R-ICSI after TFF of c-IVF, a blastulation rate of 28% could be obtained, allowing the cycle rescue in a consistent proportion of couples. What is known already Conventional IVF is to date the most indicated technique in infertile couples in the absence of male factor. However, the incidence of TFF following c-IVF, in presence of normozoospermic samples, ranges from 5 to 20%. TFF leaves experts with limited alternatives, which include cancelling the cycle with subsequent indication to proceed with ICSI in the next cycle or attempting R-ICSI in the current cycle. R-ICSI coupled with frozen embryo transfer may overcome most of the technical and biological issues associated with fresh transfer after R-ICSI, possibly representing an efficient procedure for couples experiencing TFF following c-IVF. Study design, size, duration Our retrospective study included 33 couples who underwent assisted reproduction techniques (ART) at the Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico of Milan from October 2021 to December 2022 and that experienced TFF after c-IVF, regardless the number of oocytes retrieved. Overall, TFF was reported in 7% of c-IVF cycles (33/439). An indication for male factor infertility was an exclusion criterium. World Health Organization (WHO) reference values for human semen characteristics have been adopted. Participants/materials, setting, methods Fertilization failure was considered in terms of absence of the two pronuclei and the second polar body. Out of 158 unfertilized oocytes, 128 MII oocytes were microinjected after c-IVF in the same cycle. R-ICSI consists of performing ICSI 22-24 hours after insemination with an unsuccessful c-IVF, using the same semen sample maintained at room temperature overnight. Fertilized oocytes after R-ICSI were cultured to the blastocyst stage according to our standard protocol. Main results and the role of chance The fertilization rate was 42% (95%CI: 34-51%). Fertilization failure was still observed in 9 patients (27%, 95%CI: 13-46%) after R-ICSI, with a median value of 2 [2-5] oocytes available for insemination. In the 24 patients who obtained at least one zygote, the blastulation rate was 28% (95%CI: 16-42%). A total of 15 blastocysts were cryopreserved in 10 patients on day 5 or 6 after R-ICSI. Of these 10 patients, 6 have undergone frozen/thawed single embryo transfer, and the success rate (ongoing pregnancy) was 50% (95%CI: 12-88%). Limitations, reasons for caution One of the limitations is the small sample size, since this is an emergency procedure. However, the study is still ongoing. Women were not subjected to inclusion criteria, thus fertilization failure could be attributed to several factors different from semen quality. Wider implications of the findings This study turns out to be important in light of the interesting implantation rate obtained. With the advantage of reducing both costs and psychological burden of the couple, the technique can be proposed as a rescue strategy in cases of TFF allowing to confidently increase the number of c-IVF procedure. Trial registration number not applicable