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Causes of male infertility

Ronald S Swerdloff, MD
Christina Wang, MD
Section Editor
Alvin M Matsumoto, MD
Deputy Editor
Kathryn A Martin, MD


The fertility rate in a couple is influenced by several factors. These include: the age of the female partner, age of the male partner, exposure to sexually transmitted diseases and to environmental and medical toxins, coexistent disease states, and the specific disorders described below.

While many men with male infertility have oligozoospermia (decrease in number of sperm cells in the ejaculate compared with reference ranges) or azoospermia (no sperm cells in the ejaculate), some infertile men have normal sperm counts. Over 80 percent of men with infertility have low sperm concentrations associated with a decrease in sperm motility (asthenozoospermia) and spermatozoa with normal morphology. Others may have a decrease in sperm motility and abnormal sperm morphology (teratozoospermia).

The causes of male infertility will be reviewed here. The evaluation and treatment of male infertility and issues related to unexplained infertility are discussed separately. (See "Evaluation of male infertility" and "Treatment of male infertility" and "Unexplained infertility".)


Trends in male infertility — Reports of declining sperm counts and increasing incidence of urogenital abnormalities and testicular cancer in some regions of the world have stirred public interest and concern [1-7]. Whether there is deterioration of semen quality is controversial [8-12]. Recent data in fertile men in Europe and the United States show marked differences in sperm concentration between different countries and different regions of the same country [13-15]. The role of environmental pollutants or toxins remains unclear [16,17].

A cross-sectional survey of men in the United States ages 15 to 44 years showed a prevalence of male infertility of 12 percent (95% CI 7-23) [18]. Epidemiology studies suggest that fertility rates are lower in men over age 40 years [19,20], but results from assisted reproduction technologies (ART) have not confirmed this observation [21,22]. In about 40 percent of cases of male infertility, the cause is unknown, but genetic factors may explain many of these cases in the future [18,23].


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