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Articles
Male Fertility - by Professor Chris Barratt, University of Birmingham
Male fertility issues are common and maybe increasing. Approximately 1 in 7 couples of reproductive age have difficulty conceiving a child, making sub-fertility a fairly common problem. It also seems that the incidence of ‘sub-fertility’ is increasing. Men now account for more fertility issues within couples than women. Male factors are usually diagnosed using a semen analysis.
How are sperm produced?
Sperm are produced in the testis and stored in the epididymis. On average each testis produces 50 million sperm per day – that’s 1000 sperm per heartbeat! Although the testis produces large numbers of sperm, each one takes a long time to be made. Each starts off as a stem cell in the testis and undergoes dramatic changes to form a moving cell. This transformation takes approximately 70 days. A mature sperm cell is one of the most specialized cells in the body – it is specifically made for the task in hand. It needs to be motile (to swim forward strongly to reach and penetrate the egg) and be able to deliver its DNA to the egg. This is a remarkable journey. A sperm swimming to the egg is like a man swimming across the Atlantic.
While the sperm are stored in the epididymis, they undergo further changes, which make them able to fertilize eggs. Sperm are not motile (swimming around) in the man’s body. Compared to many other animals, the human epididymis is not well designed to store a lot of sperm therefore it is recommended that men ejaculate 2-3 times per week. If sperm spend a long time in the epididymis i.e. a man does not ejaculate for a long time - the sperm that are ejaculated in the semen are damaged and probably are not any use for fertilization.
What’s in semen?
Semen is a mixture of sperm and secretions from the seminal vesicles and prostate. In fact, sperm only make up 10% of the ejaculate with the remaining seminal fluid being made up of hormones (testosterone, oestrogen, DHEA) proteins. This fluid contains substances that are thought to help the sperm in the passage through the female tract and possibly protect them against ‘attack’ by the woman’s immune system.
During ejaculation, the first part of the ejaculate contains a high concentration of spermatozoa and mainly secretions from the prostate. The latter part of the ejaculate contains secretions mainly form the seminal vesicles. In general only one teaspoonful of semen is ejaculated (5mls).
Semen Analysis
The primary method to diagnose male fertility issues is a semen analysis. This consists of producing a semen sample, which is then examined in the laboratory (using a microscope) to determine the number of sperm (sperm concentration), how they move (sperm motility) and what they look like (sperm morphology). The World Health Organization provides guidelines as to what they regard as normal and abnormal on the basis of a semen analysis.
Normal WHO guidelines
Semen volume: greater than 2mls
Sperm concentration: greater than 20 million sperm per ml in the ejaculate
Sperm motility: greater than 50% motile (greater than 10 million per ml)
Sperm morphology - no figure given. Morphology is a very controversial area. The percentage normal depends on the method used to assess normality. It is generally accepted that less than 14% normal forms are regarded as abnormal.
Are men with abnormal semen samples sterile?
The above are only guidelines and men who have abnormal semen as classified by the World Health Organization can still achieve conception. For example up to 20% of fertile men (men whose partners have naturally conceived in the last 12 months) have less than 20 million sperm per ml in the ejaculate.
