[Normal sperm].

Abstract

The evaluation of male infertility rationally begins with a study of the characteristics of the semen, notably sperm count and motility assessment. However, this examination is difficult to interpret due to the important intra- and interindividual variability of these parameters, making it impossible to determine accurately the criteria of "normality". In each given subject the characteristics of semen can be influenced by the conditions of sample collection, the length of abstinence, and any disease that may have occurred in the 3 months preceding the examination. To draw firm conclusions from one single examination would be misleading and a second examination is advised. The criteria of normality laid down by WHO are not very useful to determine the degree of fertility in males: one may speak of oligozoospermia when the sperm count is below 20 million/ml, but several recent prospective studies have shown that fertility significantly falls only below 5 million/ml. A threshold value concerning the percentage of normal forms has been established at 30-40%, whereas teratozoospermia has been defined by the WHO as from 50% onwards. Sperm count can be completed by a fine analysis of sperm motions, and this has been made possible by the development of digital microvideographic analysis techniques. However, defining norms for the main parameters of sperm motility is delicate and can only be done by teams of specialists.