Infertility is most commonly caused by problems with ovulation (the monthly release of an egg). Ovulation problems can occur as a result of a number of conditions, listed below.
The fallopian tubes are the tubes along which an egg travels from the ovary to the womb. The egg is fertilised as it travels down the fallopian tubes. When it reaches the womb, it is implanted into the womb's lining where it continues to grow. If the womb or the fallopian tubes are damaged, it may be difficult to conceive naturally. This can occur following a number of factors, outlined below.
Scarring from surgery
Pelvic surgery can sometimes cause damage, blocking and scarring to the fallopian tubes.
Cervical surgery can also sometimes cause scarring, or shorten the cervix (the neck of the womb).
Cervical mucus defect
When you are ovulating, mucus in your cervix becomes thinner so that sperm can swim through it more easily. If there is a problem with your mucus, it can make it harder to conceive.
Fibroids are benign (non-cancerous) tumours that grow in, or around, the womb. Submucosal fibroids develop in the muscle beneath the inner lining of the womb wall and grow into the middle of the womb.
Submucosal fibroids can reduce fertility, although exactly how they do this is not yet known. It is possible that a fibroid may prevent an embryo from implanting itself into your womb.
Endometriosis is a condition where small pieces of the womb lining, known as the endometrium, start growing in other places, such as the ovaries.
This can cause infertility because the new growths form adhesions (sticky areas of tissue) or cysts (fluid-filled sacs) that can block or distort the pelvis. These make it difficult for an egg to be released and become implanted into the womb. Endometriosis can cause infertility because it can disturb the way that a follicle (fluid-filled space in which an egg develops) matures and releases an egg.
Pelvic inflammatory disease (PID) is an infection of the upper female genital tract, which includes the womb, fallopian tubes and ovaries. It is often the result of a sexually transmitted infection (STI). PID can damage and scar the fallopian tubes, making it virtually impossible for an egg to travel down into the womb.
Some women choose to be sterilised if they do not wish to have any more children.
Sterilisation involves blocking the fallopian tubes to make it impossible for an egg to travel to the womb. This process is rarely reversible, and if you do have a sterilisation reversed, it will not necessarily mean that you will become fertile again.
The side effects of some types of medication and drugs can affect your fertility.
Chemotherapy – Medicines used for chemotherapy (a treatment for cancer) can sometimes cause ovarian failure, which means your ovaries will no longer be able to function properly. Ovarian failure can be permanent.
Neuroleptic medicines are antipsychotic medicines often used to treat psychosis. They can sometimes cause missed periods or infertility.
Illegal drugs such as marijuana and cocaine can seriously affect fertility, making ovulation (the monthly cycle where an egg is released from the ovaries) more difficult.
Infertility in women is also linked to age and it is an imporatant predictor of success. The biggest decrease in fertility begins during the mid thirties. Among women who are under 35, 95% will get pregnant after three years of having trying. For women who are 38, only 75% will get pregnant after three years of trying.