What causes infertility?
Possible causes
There are certain things that must happen for conception to occur, so if you are not getting pregnant, something may be going wrong at any one of these stages.
Problems with ovulation
The first stage is when the egg is released, but many things can affect ovulation. The delicate and complex system of hormones which governs the female cycle only needs to become slightly off balance for things not to work as they should:
- The egg may not mature or may not be released from the follicle
- An under-active thyroid gland can disrupt the hormonal system leading to problems with ovulation
- Another possible cause is polycystic ovarian syndrome. ‘Polycystic’ simply means ‘many cysts’ - small capsules of fluid or fat on the ovaries. These cysts secrete hormones, leading to hormone imbalance, which can affect fertility
Damaged fallopian tubes
After the egg has been released, it must travel through the fallopian tubes. One of the most common reasons for fertility problems in women is that these tubes are damaged. This could be caused by:
- A past infection
- Previous surgery in the pelvic area which has left adhesions and scarring
- Endometriosis, a condition where endometrial cells, which usually only line the walls of the uterus, grow elsewhere within the pelvis. These cells can form swellings or adhesions over the ovaries and uterus and can cause blockage of the fallopian tubes
- Any blockage of the fallopian tubes, or damage to the delicate membranes within the tubes, can severely reduce fertility
Sperm production
The next vital ingredient is for the man to produce enough sperm that are able to move forward. Problems can occur because:
- The man simply isn’t producing any sperm at all or has very low sperm levels
- The sperm are not motile (not able to swim)
- Hormone imbalances are affecting sperm production and development
- A physical obstruction at some point in the male reproductive system is blocking sperm from getting out
- The testicles have been damaged, either through injury or as a result of having mumps
- There is a varicocele (a swollen vein), although varicoceles don’t always affect fertility
- The man is suffering from retrograde ejaculation - a condition where sperm are directed into the bladder rather than the semen; this can be caused by certain drugs, previous surgery or nerve damage
- Very rarely there may be an anatomical abnormality which affects fertility
Body chemistry
The sperm must be able get through the woman’s cervical mucus. Sometimes, it seems, the body chemistry isn’t right:
- The acid secretions of the vagina may ‘kill off’ the sperm on their journey to the egg
- The woman’s cervical mucus can remain too thick for the sperm to get through
- Both men and women can have immune reactions to sperm, and produce antibodies to it. Little is known about how prevalent a problem this is, although it is one of the most promising areas of current research
Abnormal eggs or sperm
Once the sperm have reached the fallopian tube, they must be capable of fertilising the egg.
- Some sperm, even though they appear quite normal under the microscope, seem to have some chemical, possibly chromosomal, abnormality that means they are not capable of fertilisation
- As a woman ages, her eggs are more likely to contain chromosomal or chemical abnormalities, rendering fertilisation impossible
Problems in the womb
Even after fertilisation is achieved, there can be problems that prevent the egg embedding:
- Low progesterone levels can prevent the endometrium developing enough for an embryo to implant
- Occasionally physical abnormalities in the uterus (such as fibroids) prevent successful implantation
Without thorough investigation, it is impossible to tell the exact reason why a couple might not be conceiving. However, the range of possible causes shows why it is essential to find out exactly what is going wrong so that you are offered the treatment you need.
