Effects of serial thaw-refreeze cycles on human sperm motility and viability.

Cryopreservation of human spermatozoa has been used since 1954 (1). After surgical treatment, chemotherapy, or radiotherapy, permanent sterility or transient infertility of up to 5 years can occur (2). Therefore, cryopreservation is often recommended to preserve future fertility. However, sperm survival and motility are known to significantly decrease after the freeze-thaw process. Since sperm motility correlates with better pregnancy rates (3) and men presenting with systemic disease such as testicular cancer often have impaired sperm quality and quantity to begin with, these cryopreserved specimens are usually of poor quality after thawing.