Problems with sperm
BMJ Group Medical Reference
Most men with fertility problems have one or all of these problems:Low sperm count
A normal sperm sample should contain at least 40 million sperm, or at least 20 million sperm per millilitre (ml for short). Half of these should be moving. 
If you have fewer sperm than this, you have a low sperm count. This doesn't mean that you and your partner can't get pregnant, but it may take longer.
Doctors define borderline sperm quality as between 10 million and 20 million sperm per millilitre of semen, 30 percent to 50 percent of sperm moving and 4 in 100 to 14 in 100 sperm with normal appearance. 
Doctors define very poor sperm quality as less than 10 million sperm per millilitre of semen, less than 30 percent of sperm moving and less than 4 in 100 sperm with normal appearance. 
Some men have a very low sperm count or no sperm at all.  A low sperm count may be caused by an imbalance of hormones, previous damage to the testicles, or an infection of the testicles. A low sperm count sometimes runs in families. Sometimes doctors don't know the reason.Abnormal sperm
Sperm may be abnormally shaped. This may stop them moving normally or fertilising an egg. We don't know why this happens.
For more information, see More about sperm.
Hormones are chemicals that are made in certain parts of the body. They travel through the bloodstream and have an effect on other parts of the body. For example, the female sex hormone oestrogen is made in a woman's ovaries. Oestrogen has many different effects on a woman's body. It makes the breasts grow at puberty and helps control periods. It is also needed to get pregnant.
For more terms related to Fertility problems
For references related to Fertility problems click here