Since male factors are responsible for approximately 30 percent of infertility, the semen analysis is one of the earliest tests in the infertility work-up. The semen sample is usually obtained by masturbation, preferably at a facility near the laboratory.

The most important parameters checked are sperm count, motility, morphology, and the presence of inflammation cells. Sperm count, expressed as millions per cubic millimeter, should be over 20 million. Motility, or the percentage of forward-moving sperm out of the total sperm population, should be above 50 percent. Morphology, or sperm shape, is a very important criterion that best correlates with the ability of sperm to penetrate the egg. Under strict morphology criteria (called Kruger’s criteria), at least 5 percent of the sperm or more should be of normal shape. Inflammation of cells often indicate prostate or epididymal infection. They reduce the effectiveness of sperm. Inflammation should be treated, usually with antibiotics.