Effect of prolonged oocyte cryopreservation for >10 years on reproductive outcomes - a systematic review and...

Oocyte cryopreservation is essential for fertility preservation, yet the impact of prolonged cryostorage on cryosurvival, embryological and reproductive outcomes remains unclear. A systematic review and meta-analysis of 20 studies (2008-2023) from MEDLINE, Embase and Cochrane databases included 9901 patients. Nine large studies (mean cryostorage 3.76 years) were compared with 11 case studies (mean storage 10.2 years) to assess the impact of a longer period of cryostorage, as none of the large studies had ≥10 years of cryostorage. In large studies, cryosurvival was 81%, fertilization was 72%, and blastulation was 47%. Per embryo transferred (n = 9530), implantation, clinical pregnancy and live birth rates were 35%, 40% and 28%, respectively. Case studies showed comparable cryosurvival (76%), fertilization (76%) and blastulation (36%), with all reproductive outcomes exceeding 49%. A subanalysis of the case studies stratified by length of cryostorage comparing outcomes for ≥10 years (n = 6, mean 12.86 years) with <10 years (n = 5, mean 4.27 years) showed similar cryosurvival (74% versus 81%), lower fertilization (69% versus 91%; P = 0.028), comparable blastulation (37% versus 33%), and higher, although non-significant, clinical pregnancy and live birth rates (61% versus 33%). Available evidence, predominantly from case studies, suggests that prolonged cryostorage of oocytes does not compromise reproductive outcomes, although large prospective studies are needed.