A semen analysis is one of the most important tests to get at the initial visit for infertility. Sperm abnormalities are associated with approximately 40% of cases of infertility in couples. A semen analysis is done usually in the reproductive doctor's office or in certain commercial laboratories. A semen analysis looks at a variety of factors. It looks at the volume of semen produced, the sperm concentration, that is the number of sperm per milliliter of semen, the movement of the sperm, specifically what percentage of the sperm move well, and also the percentage of sperm that are of normal shape.
Sperm can come in many different types of shapes. If the shape is one that is normal, it has a good chance of penetrating the egg. If there are a lot of abnormally shaped sperm, the chance of penetration by the sperm is much lower, resulting in lower rates of fertilization. A semen analysis can also look for white blood cells indicating a possible infection. There is controversy about what is considered a normal sperm count and what are normal sperm parameters.
The definition of normal has varied over the years. Traditionally, a sperm concentration of 20 million per milliliter of ejaculate has been considered normal, although recently that number has decreased to 15 million. Having approximately one third of the sperm moving well is considered normal and at least a third of the sperm normally shaped is also considered normal. A normal semen volume is usually between two and eight milliliters. A volume of less than a milliliter is also associated with lower reproductive outcome.