Inability of a woman to conceive with a partner of normal fertility
- Increases with age; most common over the age of 35
- In rare cases, may be due to a chromosomal abnormality
- Stress, excessive exercise, and low or excess body weight are risk factors
About half of all couples who experience difficulties conceiving do so as a result of female infertility. Fertility in women decreases with age and is generally lower after the age of 35, making conception more difficult.
For conception to occur, all of the following steps must take place: ovulation (the production and release of a mature egg by an ovary), fertilization of the egg by a sperm, transport of the fertilized egg along the fallopian tube to the uterus, and implantation of the fertilized egg in the lining of the uterus. If any stage does not occur or is interrupted, conception cannot take place.
What are the causes?
There are a number of fertility problems in females that may affect one or more of the processes required for conception. The problems can develop at different stages of conception.
Problems with ovulation
A common cause of female infertility is failure of the ovaries to release a mature egg during each monthly cycle. Ovulation is controlled by a complex interaction of hormones, including those produced by the hypothalamus (an area of the brain), the pituitary gland, and the ovaries. A common and usually treatable cause of female infertility is polycystic ovary syndrome, which may cause a hormonal imbalance that prevents ovulation from taking place. Very rarely, disorders of the thyroid gland, such as hypothyroidism, may also lead to a hormonal imbalance that can affect the frequency of ovulation. Pituitary gland disorders, such as prolactinoma, a noncancerous tumour, may cause a similar imbalance. Ovulation does not always occur in some women for reasons that are unclear. In some cases, women who have been using oral contraceptives for a number of years may take time to re-establish a normal hormonal cycle after discontinuing them. Excessive exercise, stress, and obesity or low body weight may be other factors that affect hormone levels and cause temporary infertility.
Premature menopause also results in a failure to ovulate. It can occur for no apparent reason or may be the result of pelvic surgery, chemotherapy, or radiotherapy. In rare cases, the ovaries do not develop normally due to a chromosomal abnormality, such as Turner’s syndrome.
Problems with egg transport and fertilization
The passage of the egg from the ovary to the uterus may be impeded by damage to one of the fallopian tubes. This damage may be due to pelvic infection (see Pelvic inflammatory disease), which may in turn result from a sexually transmitted infection such as chlamydial infection. Such disorders may exist with no symptoms and may be detected only if you have difficulty conceiving.
Endometriosis, a condition that can lead to the formation of scar tissue and cysts within the pelvis, may prevent the passage of an egg.
Problems with implantation
If the lining of the uterus has been damaged by an infection, such as gonorrhoea, the implantation of a fertilized egg may not be possible. Hormonal problems may also result in the uterine lining not being adequately prepared for successful implantation. Noncancerous tumours that distort the uterus (see Fibroids) and, rarely, structural abnormalities present from birth may make it difficult for a fertilized egg to embed itself in the uterine lining.
What might be done?
Your doctor will ask you about your general state of health, your lifestyle, your medical and menstrual history, and your sex life before recommending particular tests and treatments.
Most causes of female infertility can now be identified through testing. You can find out if and when you ovulate by using an ovulation prediction kit, available over the counter, or by recording your body temperature daily (see Using contraceptives). If your doctor suspects that you are not ovulating regularly, you may have to undergo repeated blood tests during your menstrual cycle to assess the level of the hormone progesterone, which normally rises after ovulation.
If tests show that you are not ovulating, you may need further blood tests to check the levels of certain hormones, including prolactin, and drugs may be prescribed to stimulate ovulation (see Drugs for infertility). However, if you are ovulating, the next step is for your doctor to find to find out whether your partner is producing sufficient normal sperm. This can be done by microscopic examination of samples of semen (see Semen analysis).
If you are ovulating normally and your partner’s sperm are healthy, your doctor will check if there is a problem preventing the egg and sperm from meeting. He or she may arrange for further investigations to look for a blockage in the fallopian tubes or an abnormality of the uterus. One such test is laparoscopy, in which an endoscope containing a camera is inserted through a small incision in the abdomen. Another test that may be used to look for abnormalities in the fallopian tubes or uterus is hysterosalpingography, in which a dye is injected through the cervix and X-rays are taken as the dye enters the reproductive organs.
The treatment depends on the problem. For example, a blockage of the fallopian tubes may sometimes be corrected by microsurgery, and endometriosis may be treated with drugs (see Sex hormones and related drugs) or, in some cases, by laparoscopy.
What is the prognosis?
Treatments for female infertility have greatly increased the chance of pregnancy. Success rates vary, depending on the cause of the infertility and the type of treatment carried out. Fertility drugs stimulate ovulation in 1 in 3 women, but there is a risk of multiple pregnancy. Microsurgery to correct a tubal blockage can be successful but this procedure increases the risk of ectopic pregnancy, a pregnancy that develops outside the uterus, usually in a fallopian tube. Success rates for assisted conception methods range from 15 to 30 per cent for each individual treatment.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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