The complex and finely balanced processes involved in egg and sperm production, and fertilisation create numerous opportunities for something to go wrong.

Infertility is usually defined as the inability of a couple to conceive after one year of unprotected intercourse. However, younger couples may be encouraged to wait for up to two years by some doctors before seeking treatment, while women over 35 or those with certain medical conditions, such as diabetes, should only wait six months.

About one in six couples concerned end up seeking help. Within this group the problem is found to lie with the woman in up to 40 per cent of cases, and with the man about a third of the time. In the remaining cases around 15 to 30 per cent of both partners are found to have reduced fertility and in five to 10 per cent of couples the cause cannot be determined.

Male factors

• Sperm potency: The vast majority of cases of male infertility are due to a low sperm count, which is generally associated with a high rate of sperm defects (size, shape and movement).
  
  Hormonal imbalances related to follicle stimulating hormone (FSH) and luteinising hormone (LH), do occur in men, but are not very common. They may affect the development of sperm and account for some sperm abnormalities.
  
  There is also some evidence to suggest that male sperm counts are declining in many populations. The exact reasons are unclear, but are thought to be environmental.
  
  
  
• Testicular failure: Some men are found to have no sperm in their semen. This could be due to a failure to ejaculate or a failure of the testes to produce sperm. The testes may have been damaged due to a poor blood supply, injury or even a case of adult mumps. Other causes include hormonal problems and genetic defects.
  
  
• Varicocele: These are varicose veins in one or both scrotums, and are the most common anatomical abnormality in infertile men. A varicocele results in the pooling of blood and higher temperatures in the scrotum.
  
  
• Tubal blockage: Damage as a result of infections can prevent the sperm from getting into the semen. Occasionally the ejaculate of some men is diverted into the bladder.
  
  
• Sperm antibodies: A small group of men actually produce antibodies against their own sperm. The cause is not totally clear and is thought to account for around 10 per cent of unexplained male infertility.

Female factors

• Hormonal / ovulation: Hormonal problems, related to follicle stimulating hormone and luteinising hormone affect follicular development as well as ovulation.
  
  Problems with ovulation are the most common cause for female infertility and account for up to a third of all cases. A woman may be anovular (complete failure to ovulate) or have infrequent or irregular ovulation.
  
  Polycystic ovarian disease can also lead to hormonal imbalances, creating a number of problems, particularly affecting ovulation.
  
  The female reproductive system can also fall prey to problems in progesterone secretion.
  
  
• Tubal problems: Damage to the fallopian tubes is another common reason for infertility, preventing the egg from travelling down affecting fertilisation or passage to the uterus.
  
  
• Uterine problems: A key problem in the uterus is that of endometriosis, where developing cells from the endometrium break away and stick to the ovaries and fallopian tubes affecting the way they function. Up to 70 per cent of women with endometriosis experience some degree of infertility.
  Fibroids and polyps in the uterus can also cause problems with fertility.
  
  
• Cervix / vaginal problems: Structural abnormalities of the vagina or cervix can affect fertility as can the physical characteristics of the cervical mucus. The mucus can be hostile to sperm, perhaps containing antibodies or thick enough to block the movement of the sperm.

Joint infertility problems

Of the number of cases of infertility where the problem lies with both partners, some of the causes may be straight forward and quite simple to remedy. As the window of opportunity to fertilise an egg is quite limited in a woman’s monthly cycle, the frequency and timing of intercourse may be factors.

• Frequency: A couple may simply not be having intercourse frequently enough to coincide with the woman’s most fertile phase.  Sperm can live about 48 hours in the woman’s reproductive tract and only during this time can they fertilise an egg.
  
  Intercourse every two to three days around the time of ovulation should be the optimum frequency for fertilisation.
  
  
• Timing: Equally, the problem could be due to missing the most fertile phase, particularly where the woman’s cycle is not regular, or is longer or shorter than the average 28 days.
  
  
• Technique:  Some cases have been found to be related to technique, where the sperm is not deposited high enough in the vagina to have a chance of passing through the cervix.
  
  
• Age: Fertility is also reduced with increasing age, especially in women.  Maximum fertility in women is between the ages of 15 and 24 and by the time a woman reaches 50, most of the remaining eggs she was born with will have been reabsorbed by the body, curtailing the production of oestrogen and progesterone.
  
  In men, testosterone levels can decline with age but not in the dramatic manner seen in women. Men continue to produce sperm, but their motility can reduce with advancing age.