Semen and sperm quality

Bulbourethral and urethral glands
The secretions of these glands lubricate the male reproductive tract, but they may also contain antibodies that can affect fertility. These anti-sperm antibodies can prevent the spermatozoa moving properly and prevent them from fertilising the ovum (egg).

What is normal semen?
Semen is usually white or grey, but can occasionally appear yellowish. Pink or red semen suggests that blood is present. Although this is only rarely due to a serious health problem, men with semen that seems bloodstained should seek advice from their family doctor.

Semen clots almost immediately after ejaculation, forming a sticky, jelly-like liquid. It will liquefy again in 5 to 40 minutes. It is quite normal for semen to form jelly-like globules and this does not indicate any health or fertility problem. Failure of clotting and subsequent liquefaction can cause fertility problems.

The average volume of semen produced at ejaculation is 2 to 5ml. Volumes consistently less than 1.5ml (hypospermia) or more than 5.5ml (hyperspermia) are probably abnormal. Lower volumes may occur after very frequent ejaculation and higher volumes are seen after prolonged abstinence.

The World Health Organisation provides a definition of a 'normal' sperm count:

• the concentration of spermatozoa should be at least 20 million per ml.
• the total volume of semen should be at least 2ml.
• the total number of spermatozoa in the ejaculate should be at least 40 million.
• at least 75 per cent of the spermatozoa should be alive (it is normal for up to 25 per cent to be dead).
• at least 30 per cent of the spermatozoa should be of normal shape and form.
• at least 25 per cent of the spermatozoa should be swimming with rapid forward movement.
• at least 50 per cent of the spermatozoa should be swimming forward, even if only sluggishly.

Measuring sperm count is a very technical business and results can be affected by many factors, including the length of time between ejaculation and semen sample analysis, and how the sample is kept when being transported to the lab.

There can be enormous variation in sperm count in an individual, even over a few days. It is important that at least two, preferably three or more, samples are analysed, each at least two to three weeks apart. A single sample is inadequate to assess semen quality.

Sperm count is only an indication of fertilising capacity and a normal count does not guarantee success.

Is male fertility declining?
Numerous articles have suggested that sperm counts are falling and that male fertility is in decline. One of the most widely reported was a 1992 paper by Carlson and collaborators1 that looked back at 61 research papers published since 1938, and concluded that the average sperm count had dropped by 42 per cent. However, their analysis was flawed in many ways and their conclusions cannot be considered reliable.

Several more retrospective studies of semen quality have been published since, with conflicting results. Some suggest that sperm counts are declining, others that there is no change. Even if sperm counts are falling, the effect on fertility is also unclear. At present, there is no clear evidence one way or the other.

Could environmental factors be affecting male fertility today?
Many more environmental factors that can affect male fertility exist today than 50 years ago. The factors include:

• endocrine disrupters
• toxic pollutants
• sexually transmitted infections
• zinc deficiency
• alcoholism
• smoking
• anabolic steroid use
• ionising radiation.

• Adopt a healthy lifestyle, with a balanced diet and regular exercise.
• Don't smoke or use recreational drugs.
• Don't drink alcohol, or keep alcohol consumption within recommended limits.
• Try to avoid exposure to industrial and occupational hazards by following safety procedures and wearing protective clothing when provided. Your employer has a legal responsibility to provide information on occupational health risks and to ensure employees have a safe and healthy working environment.
• Avoid exposure to sexually transmitted diseases by adopting safer sexual practices, such as using condoms and reducing your number of partners.

An interesting research study from the Netherlands showed that wearing tight leather trousers and tight plastic underwear together affected sperm motility, but neither had an effect alone.

Some evidence suggests that stress reduces semen quality, probably due to hormonal changes in the body that result from stress.

The causes of stress in modern life are legion and concerns over fertility or failure to conceive are very important causes of stress. If you are concerned that you have a fertility problem, it is sensible to seek advice from your family doctor.

The chance of conception in a healthy, young couple is about 20 per cent per month, so a delay of three to six months before conceiving is not unusual. It is reasonable to request an initial assessment after six months of regular unprotected intercourse without conception.