Thawed human sperm quality is influenced by the volume of the cryopreserved specimen.

OBJECTIVE: To test the effect of sperm specimen volume in the freezing-thawing process on specimen quality. DESIGN: Experimental prospective study. SETTING: Tertiary academic medical center. PATIENT(S): Fifty high-quality sperm donors donated ∼3 times each. Sperm samples were split into two aliquots and frozen in volumes of 0.25 mL and 0.5 mL. INTERVENTION(S): Semen analyses. MAIN OUTCOME MEASURE(S): Eight sperm quality parameters of thawed specimens. RESULT(S): Thawed 0.5-mL specimens had a higher percentage of motility and viability, progressive motility concentration, percentage of cells with high mitochondrial membrane potential, and intact chromatin compared with 0.25-mL specimens. Although there were fewer cells with intact acrosomes in the 0.5-mL thawed samples, they had a similar ability to respond to ionophore by acrosome reaction as the 0.25-mL specimens. Both groups had similar percentages of cells with oxidative stress and numbers of cells that bound to the zona pellucida. The remaining air volume in the straw and freezing medium composition had a minimal effect on tested parameters. CONCLUSION(S): Better quality thawed human sperm was achieved after cryopreservation of high volumes compared with low volumes of specimens. Air volume in the straw had no influence on specimen quality.