Three factors that lower male fertility.

• Position: Your Life - Brief article

Working in a physically demanding job, having high blood pressure, and taking multiple medications are among health risks that may undermine a man's fertility, according to a study by researchers at Stanford University, Palo Alto, Calif.

"Nearly 15% of U.S. couples do not become pregnant in their first year of trying," points out Michael L. Eisenberg, the study's principal investigator and director of Male Reproductive Medicine and Surgery. "Male infertility plays a significant role, and our aim is to explore the influence of environmental factors and health status on semen quality," which is a measure of a man's ability to achieve fertilization and is based on the number, shape, and movement ability of sperm.

The researchers found that 13% of the men who reported heavy work-related activity had lower sperm counts, compared to six percent of the men who reported no workplace...