Is there sufficient number of mobile sperm cells for fertilization?

Male fertility may be examined with a microscopic examination of the sperm where special attention is paid to the quantity and the motility of the sperm cells. Based on this examination it is possible to give an evaluation concerning the fertility of the man. The quality of the semen may vary considerably over time. A reduced sperm count and lower mobility of the sperm cells may be due to infectious diseases (such as chlamydia or the mumps), a testicular injury, certain medication, use of anabolic steroids and dissolvents, or smoking, but often the cause remains unclear. In addition, hereditary causes are a possible reason for a low sperm count or poor motility of the sperm.