An explanation for the increasing incidence of testis cancer: decreasing age at first full-term pregnancy.

Abstract
For unknown reasons, the incidence of cancer of the testis has increased substantially among white male populations of several European countries, the United States, Australia, and New Zealand (1). In Japan, the rates of testicular cancer have increased recently as well (2). An increase in the rate in white populations was first noted among men born after 1920, but this increase was not consistently sustained for men born between 1930 and 1945 (1). However, for men born in the 1950s onward, the increase in incidence has been uninterrupted. Explanations for this secular increase have been elusive. To some investigators, reports of a concomitant decrease in sperm counts in young men have suggested that an environmental exposure (e.g., pesticides and plant phytoestrogens) might be responsible (3).