Objective: To determine, among the following variables, the predictors of sperm fertilization potential of a given semen sample: sperm count, eight sperm velocity characteristics determined by computer-assisted semen analysis, the sperm morphology score determined by strict criteria, and the hypo-osmotic swelling (HOS) test, using the IVF model.
Design: Data from 58 couples attending the assisted conception unit for conventional IVF treatment were analyzed retrospectively by simple linear regression and multiple stepwise regression analysis, taking the fertilization rate as the dependent factor.
Results: The mean sperm velocity and the strict sperm morphology assessment were the only parameters showing significant correlation with the fertilization rate. A minimum sperm velocity of 13 microm/s and a minimum strict sperm morphology of 2% were necessary to achieve fertilization in 50% of the oocytes. The results of the HOS test did not correlate with the fertilization rate. An equation was devised to calculate the expected fertilization rate based on the mean sperm velocity and the strict morphology score, and can be used to counsel patients prior to assisted conception.
Conclusions: The mean sperm velocity and strict sperm morphology evaluation are good predictors of fertilization potential, but the HOS test is not.