Male factor infertility is solely responsible for about 20% of infertile couples and is contributory in another 30 to 40%. Therefore, it is critical that both partners are evaluated. Additionally, it is important to understand that a normal result of a semen analysis does not rule out all male factors that may be causing or contributing to the infertility.
In nearly all cases there is no way to predict the fertility of a man without having a semen analysis performed. Because day-to-day sperm production can be quite variable, if the first semen analysis returns abnormal it is usually recommended that a second semen analysis be performed. Male fertility gradually decreases with increasing age, however unlike the female, with a limited supply of eggs, the male continues to make sperm throughout his life. Medical studies suggest that men older than age 45 take significantly longer to successfully father of pregnancy even with a younger partner.
There is a long standing World Health Organization system defining “normal” values for semen analysis.