Fertility is reduced naturally as men and women age. About fifteen percent of all couples in the United States are infertile or unable to have a child after one year of regular, unprotected intercourse. This inability to have a child may be the only sign or symptom of male infertility. Male infertility is a problem for about forty percent of infertile couples. Not enough sperm being produced or problems with the sperm can be caused by a severe injury to the testicles, alcohol or drug abuse, or scar tissue from sexually transmitted diseases or surgery.
Fever can also cause temporarily lowered sperm production.
A varicocele or enlarged vein in the scrotum may cause an increase in temperature in the area of sperm production. This may cause abnormal sperm to be produced. Infections with sexually transmitted diseases can cause infertility by damaging reproductive organs and blocking sperm pathways. The drug was given to pregnant women to prevent miscarriages from 1940 to 1971. As a result, children were exposed to the drug while in the womb.