The donors are selected by sperm banks according to the parameters of sperm concentration per milliliter and the percentage of sperm cells in motion. However, we must take into consideration that in all men the vast majority of sperm are flawed for the simple reason that production of 100 million cells per day does not allow quality control. Therefore, even when the donor has the most impressive general sperm parameters, it is quite possible that there are no normal sperm cells, or that their percentage is so low that the chance that a normal cell will fertilize the egg will be 0. To overcome this, we offer the [ morphological sorting of sperm] , during which we choose the most proper spermatozoa for fertilization, significantly increasing its chance of success.