Humans produce relatively low numbers of viable sperm as compared to other mammals. As many as one in five healthy young men between the ages of 18 and 25 produce abnormal sperm counts. Even the sperm they produce is often of poor quality.
Men also suffer a high incidence of reproductive problems, from congenital defects to cancer and impotency. In fact, an increasing number of men are now finding themselves childless. Among the one in seven couples now classed as infertile, the "male factor" has been found to be the most commonly identified cause.
There is now an emerging consensus among experts that whatever it is that is increasing the problems of male infertility, it apparently starts in the womb. It is not the mens' lifestyle that is problem, but that of their mothers. The process of sperm production, called spermatogenesis, starts in adolescence, but the groundwork is laid down in the few months after birth.
"It's most likely a reflection of the fact that many environmental and lifestyle changes over the past 50 years are inherently detrimental to sperm production," The Independent quoted Professor Richard Sharpe, fertility research expert at the Medical Research Council as saying. "It may be that different factors come together to have a combined effect."
Several studies point to a connection between early development in the womb and male reproductive problems in later life, especially low sperm counts.