The most common cause of male infertility is low sperm count or absence of sperm in the semen.

Causes of low sperm count may include

* Hormonal problems in the testicles or pituitary gland.

* Genetic factors.

* Testicular injury, infection or failure.

* Drug use.

Environmental factors including chemical pollution and exposure to radiation. Medical conditions such as a varicocele in the testicles, blocked ejaculation due to a surgical vasectomy, absence or blockage of a vas deferens due to birth defect or infections (The vas deferens is a narrow, muscular tube that connects the testicles to the prostate gland), retrograde ejaculation (the ejaculation of semen into the bladder rather than out through the penis), Chromosomal problems.
Problem caused by the immune system after an infection, vasectomy or injury to the testicles. The man may develop, an auto-immune response in which his immune system treats his sperm as 'foreign' and produce antibodies against them.