Live birth rates are unaffected by sperm cryopreservation time
Retrospective analysis of over 100,000 sperm donor samples at the Hunan Sperm Bank (Hunan, China) has found that specimens cryopreserved for 15 years did not negatively impact on live birth rates, compared to samples preserved for six months.
Many countries currently have in place a restriction on the duration of cryopreservation of sperm samples. This is due to the assumption that long term cryopreservation may impact on sperm survival rates following thawing, which may impact birth rates resulting from use of these samples.
New retrospective research, however, has determined that the length of time sperm samples are cryopreserved does not impact on live birth rates.
Researchers in China analyzed 119,558 semen samples from the Hunan Sperm Bank (Hunan, China); the samples were categorized according to duration of cryopreservation. Three groups of samples were specified: those frozen for between 6 months and 5 years, those frozen for between five and 10 years and those frozen for between 11 and 15 years.
The results of the study, presented at the 35th annual European Society of Human Reproduction and Embryology meeting (ESHRE, Vienna, Austria) found that, following thawing, survival rates of sperm from samples frozen for up to 15 years were lower than those of samples frozen for a minimum of 6 months (74% survival versus 85% survival).
Live birth rates, however, resulting from using these samples for insemination or IVF, were unaffected by duration of sample freezing; live birth and IVF success rates were similar across all three groups.
It is important to note, however, that all sperm donors donating at the Hunan Sperm Bank must undergo extensive screening; donors must be in good mental and physical health, and display no familial genetic disease history. This may impact of the representativeness of the data of the general population.
Chuan Huang, from the Changsa-Hunan Sperm Bank in China, commented that despite this extensive screening procedure, the study still clearly demonstrates “that the long-term storage of sperm does not appear to affect live birth rates”.
Currently, many countries restrict the duration of sperm sample cryopreservation to 10 years. Despite the lack of supporting clinical outcome evidence for this restriction, the small, but statistically significant reduction in sperm survival rates observed between the three groups in this study, causes Huang to recommend that “…sperm banks should provide sperm in their order of cryopreservation…”.