AnswerIn men, the problems are mainly with the making of sperm or with getting the sperm to reach the egg. These problems with sperm may be present by birth or it could develop later in life due to lifestyle changes, illness or injuries. Few men produce no sperm or produce very few sperm. As per research lifestyle can influence the number and quality of a man's sperm dramatically. Alcohol and drugs can provisionally reduce the sperm quality. Other environmental toxin, that includes pesticides and lead, can also cause infertility in men.The main causes for males may include:Sperm not being produced in sufficient numbers, or not at all (Azoospermia);Sperm being obstructed from ejaculation;Sperm that does not swim very well in the female reproductive system restricting its ability to reach an