Infertility in men is most often caused by:
Problems in sperm production – producing too few sperm(oligospermia) or none at all(azoospermia).
Problems with the sperm’s ability to reach the egg and fertilize it – abnormal sperm shape or structure prevent it from moving correctly.
Problem in sperm release – At times due to obstruction in the duct carrying the sperm from the testis to the ejaculate (obstructive azoospermia ).Problems with erection and ejaculation also contribute to male infertility.
Sometimes a man is born with the problems that affect his sperm. Other times problems start later in life due to illness or injury.