The causes of infertility vary from person to person.
The most common causes of infertility are detailed below.
A problem in any one of a number of key processes can result in infertility. Male and female factors can exist in isolation or combination and fertility investigations, diagnoses and treatment should always be considered in the context of the couple.
Sperm problems will contribute to about 40% of infertility cases. The normal working of the male reproductive system involves first the production of sufficient numbers of functional sperm cells and then the delivery of these sperm to the ejaculate. Key to the diagnosis of male infertility is a semen analysis, which assesses primarily sperm numbers, sperm movement and sperm form.
Dysfunction of the female reproductive organs is also apparent in around 40% of infertile couples. The most common identifiable causes of female fertility problems are outlined below:
• Ovulatory dysfunction, (or anovulation) where an egg is not released from the ovary every month, is the single most common cause of female infertility. Predominantly anovulation is caused by hormonal imbalances such as Polycystic Ovarian Syndrome (PCOS) but ovarian scarring and premature menopause can also result in failure to ovulate.
• Tubal disease, comprising anything from mild adhesions to complete blockage of the fallopian tubes, prevents fertilised eggs from travelling from the site of fertilisation to the uterus. It may also prevent the sperm from reaching the egg. Normal uterine implantation can therefore not occur. The main causes of tubal infertility are pelvic infections caused by bacteria such as chlamydia, previous abdominal disease or surgery and ectopic pregnancy.
• Endometriosis is characterised by excessive growth of the lining of the uterus. These endometrial cells can extend as far as the outside of the fallopian tubes, the ovaries and the bladder. As they respond to hormones the same way as they would do in the uterus, that is by growing and shedding cyclically, endometriosis can cause both fallopian tube and ovarian scarring.
Some people may not have difficulty conceiving, but have suffered from miscarriages. This is obviously extremely distressing for the couples involved. Our miscarriage clinic can help investigate these issues and attempt to help couples with any future pregnancy.
The following other factors may also be responsible for infertility in a smaller proportion of cases:
• Genetic abnormalities within eggs, sperm or both
• An abnormal uterine cavity, including the presence of fibroids or polyps
• Immunological infertility, whereby either the male or female partner produces anti-bodies against sperm cells or implantation of an embryo
• Abnormal cervical mucus which hinders the passage of sperm to the uterus and fallopian tubes
Even when investigations have been extensive, some couples will have no reason with which to explain their infertility. This can often be a frustrating diagnosis. In these cases the duration of the infertility is the best parameter by which to judge the chances of future natural conception; the longer the time of infertility then the sooner intervention should be considered.