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A semen analysis, measuring the volume of the ejaculate, the density of spermatozoa (sperm cells, or just sperm) in it (expressed as so many million sperm per milliliter), the proportion of sperm swimming normally (the motility), and the proportion with a normal shape. A normal sperm count consists of a volume of more than 1 ml; a density of more than 20 million per ml; a motility of more than 50 percent; and normal forms of more than 50 percent (casual examination) or more than 14 percent (critical examination by the strict criteria recently advocated by the World Health Organization). For the effects of frequent sex on sperm counts (as well as other aspects of collecting semen for the test), see pages 52 to 54 of Overcoming Infertility. For more on the question of a possible world-wide decline in sperm counts over the last generation, see pages 120 to 123 and the box, Lessons from Wildlife … |
