Kruger strict morphology and post-thaw progressive motility in cryopreserved human spermatozoa

The purpose of this prospective study was to evaluate Kruger strict morphology and conventional semen analysis in predicting cryosurvival and the progressive motility recovery rate of frozen spermatozoa. Our study included 56 semen samples with >10 million spermatozoa per ejaculate. The main outcome measures were conventional semen analysis, strict morphology analysis by the Kruger method, cryosurvival rate and post-thaw sperm motility. A significant reduction in sperm motility after cryopreservation was demonstrated. The freeze-thawing process caused a 66% reduction in rapid progressive motile spermatozoa, a 45% reduction in slow progressive motile spermatozoa and a 2% reduction in nonprogressive motile spermatozoa. The cryosurvival and progressive motility recovery rates were not correlated with parameters of conventional semen analysis, such as sperm concentration, motility, WHO morphology and total motile count, but the progressive motility recovery rate was significantly correlated with the percentage of spermatozoa exhibiting Kruger normal morphology (P = 0.028). The recovery rate of rapidly progressive motility was profoundly decreased compared with slow progressive motility following the frozen-thaw procedure of semen. Kruger strict morphology assessment was a better predictor of the progressive motility recovery rate following the freezing-thaw procedure than parameters of conventional semen analysis.