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S Canosa, D Cimadomo, A Conforti, R Maggiulli, A Giancani, A Tallarita, F Golia, G Fabozzi, A Vaiarelli, G Gennarelli, A Revelli, F Bongioanni, C Alviggi, F M Ubaldi, L Rienzi, SIERR

Journal of Assisted Reproduction and Genetics, Received16 December 2021, Accepted15 January 2022, Published04 February 2022


Purpose: Few studies explored whether prolonged cryo-storage after vitrification affects embryo competence and perinatal outcomes. This systematic review and meta-analysis aims at highlighting any putative impact of cryo-storage duration on cryo-survival, miscarriage, live birth and major malformations.

Methods: A systematic review was performed using MEDLINE (PubMed), ISI Web of Knowledge, Scopus and Embase databases up to June 2021. Data were combined to obtain a pooled OR, and meta-analysis was conducted using a random effects model. Out of 1,389 screened abstracts, 22 papers were assessed for eligibility, and 5 studies were included (N = 18,047 embryos). Prolonged cryo-storage was defined as > 12 months (N = 3389 embryos). Subgroup analysis was performed for untested vitrified cleavage stage embryos (N = 1739 embryos) and for untested and euploid vitrified blastocysts (N = 13,596 and 2712 embryos, respectively).

Results: Survival rate, miscarriage, live birth and major malformation rates were all similar in the two groups.

Conclusion: These data further support the safety of long-term cryo-storage of human embryos beyond 12 months. This is reassuring for good prognosis patients with surplus embryos, couples seeking a second child from supernumerary embryos and women postponing the transfer for clinical or personal reasons.


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