Influence of Sperm Processing on the Fertilizing Capacity and Recovery of Motile Sperm from Thawed Human Semen

Artificial insemination programs now rely almost exclusively on frozen semen preparations as their source of sperm. Unfortunately, several reports indicate that conception rates using frozen-thawed semen are inferior to freshly ejaculated specimens. The present study was designed to investigate the fertilizing capacity of sperm and the recovery of motile sperm from thawed semen following different sperm processing methods. Washed resuspended pellets contained sperm with at least the same fertilizing potential as sperm from swim-up techniques. However, the recovery of motile sperm from the pellets was more than 3 times greater than from the swim-up techniques. Percentage motility, progressive velocity, and amplitude of lateral head displacement were generally higher in the sperm from swim-up techniques than in the sperm from the pellets, despite equivalent fertilizing potentials. It can be argued from these results that washed resuspended sperm preparations provide a significantly greater number of motile sperm without a loss in fertility when compared to sperm from swim-up techniques. Accordingly, this study raises questions about the use of the sperm swim-up as a procedure for processing thawed semen for use in intrauterine insemination in which maximal numbers of motile sperm are required. It also demonstrates the need to identify new methods for processing frozen-thawed specimens for assisted reproductive procedures.