Male infertility refers to a sexually mature males inability to impregnate a fertile female. In humans it accounts for 40–50% of infertility. It affects approximately 7% of all men. Male infertility is commonly due to deficiencies in the semen, and semen quality is used as a surrogate measure of male fecundity. More recently, advance sperm analyses that examine intracellular sperm components are being developed. Age considerations
There is a decrease in sperm concentration as men age: 90% of seminiferous tubules in men in their 20s and 30s contain spermatids, whereas men in their 40s and 50s have spermatids in 50% of their seminiferous tubules, and only 10% of seminiferous tubules from men aged > 80 years contain spermatids. In a random international sample of 11,548 men confirmed to be biological fathers by DNA paternity testing, the oldest father was found to be 66 years old at the birth of his child; the ratio of DNA-confirmed versus DNA-rejected paternity tests around that age is in agreement with the notion of general male infertility above age 65–66. Causes
Factors relating to male infertility include:

Immune infertility
Antisperm antibodies (ASA) have been considered as infertility cause in around 10–30% of infertile couples. ASA production are directed against surface antigens on sperm, which can interfere with sperm motility and transport through the female reproductive tract, inhibiting capacitation and acrosome reaction, impaired fertilization, influence on the implantation process, and impaired growth and development of the embryo.
The sample should never be obtained through coitus interruptus for several reasons:

Some part of ejaculation could be lost. Bacterial contamination could happen. The acid vaginal pH could be deleterious for sperm motility.Also is very important to label the sample correctly the recipient with patient identification, date, hour, abstinence days, among other data required to be known. The volume of the semen sample (must be more than 1.5 ml), approximate number of total sperm cells, sperm motility/forward progression, and % of sperm with normal morphology are measured. It is possible to have hyperspermia (high volume more than 6 ml) or Hypospermia (low volume less than 0.5 ml). This is the most common type of fertility testing. Semen deficiencies are often labeled as follows:

Oligospermia or oligozoospermia – decreased number of spermatozoa in semen
Aspermia – complete lack of semen
Hypospermia – reduced seminal volume
Azoospermia – absence of sperm cells in semen
Teratospermia – increase in sperm with abnormal morphology
Asthenozoospermia – reduced sperm motility
Necrozoospermia – all sperm in the ejaculate are dead
Leucospermia – a high level of white blood cells in semen
Normozoospermia or normospermia – It is a result of semen analysis that shows normal values of all ejaculate parameters by WHO but still there are chances of being infertile. This is also called as unexplained InfertilityThere are various combinations of these as well, e.g. Teratoasthenozoospermia, which is reduced sperm morphology and motility. Low sperm counts are often associated with decreased sperm motility and increased abnormal morphology, thus the terms "oligoasthenoteratozoospermia" or "oligospermia" can be used as a catch-all.