Clinical benefit for cryopreservation of single human spermatozoa for ICSI: A systematic review and meta-analysis

Systematic reviews have focused on sperm recovery and post-thaw parameters after cryopreservation, but there is no information on the associated clinical outcomes. In recent years, an increasing number of studies have reported cryopreservation of a single sperm due to the importance of fertility preservation.

To assess whether the cryopreservation of single human spermatozoa improves clinical outcomes in patients with azoospermia or severe oligospermia.

We conducted an extensive literature search using the following databases: CENTRAL, CNKI, Cochrane Systematic Reviews, EMBASE, MEDLINE, PUBMED, and Web of Science for relevant studies published through December 31, 2019. We calculated the pooled proportions of cryopreservation of a single human spermatozoon to assess the recovery, survival, fertilization, pregnancy, miscarriage, and delivery rates. Subgroup analyses were performed for the following covariates, (a) different carriers, (b) year of publication, and (c) source of sperm.

We included 25 studies, which included 13 carriers. The pooled proportion of recovery rate of spermatozoa cryopreserved was 92% (95% CI, 87%-96%), and the survival, fertilization, pregnancy, miscarriage, and delivery rates were 76% (95% CI, 69%-83%), 63% (95% CI, 58%-67%), 57% (95% CI, 39%-74%), 12% (95% CI, 0%-33%), and 40% (95% CI, 12%-71%), respectively. Based on the subgroup analysis, the recovery and survival rates of frozen spermatozoa in a subgroup of different carriers were statistically significant. In the past decade, frozen single human spermatozoon technology has improved the recovery rates of frozen-thawed spermatozoa. However, the differences in clinical outcomes of frozen spermatozoa in subgroups of different sources of sperm were not statistically significant.

The techniques for single human spermatozoa are feasible and efficient and may benefit patients with severe oligospermia or azoospermia.