What Causes Female Infertility?
Causes of Failure to Ovulate
Ovulatory disorders are one of the most common reasons why women are unable to conceive, and account for 30% of women's infertility. The causes of failed ovulation can be categorized as follows:
In approximately 50% of the cases of anovulation, the ovaries do not produce normal follicles inwhich the eggs can mature. Ovulation is rare if the eggs are immature and the chance of fertilization becomes almost nonexistent. Polycystic ovary syndrome, the most common disorder responsible for this problem, includes symptoms such as amenorrhoea, hirsutism, anovulation and infertility. This syndrome is characterized by a reduced production of FSH, and normal or increased levels of LH, oestrogen and testosterone. The current hypothesis is that the suppression of FSH associated with this condition causes only partial development of ovarian follicles, and follicular cysts can be detected in an ultrasound scan. The affected ovary often becomes surrounded with a smooth white capsule and is double its normal size. The increased level of oestrogen raises the risk of breast cancer.
The hypothalamus is the portion of the brain responsible for sending signals to the pituitary gland, which, in turn, sends hormonal stimuli to the ovaries in the form of FSH and LH to initiate egg maturation. If the hypothalamus fails to trigger and control this process, immature eggs will result. This is the cause of ovarian failure in 20% of cases.
The pituitary's responsibility lies in producing and secreting FSH and LH. The ovaries will be unable to ovulate properly if either too much or too little of these substances is produced. This can occur due to physical injury, a tumor or if there is a chemical imbalance in the pituitary.
This presents a rare and as of yet unexplainable cause of anovulation. Some women cease menstruation and begin menopause before normal age. It is hypothesized that their natural supply of eggs has been depleted or that the majority of cases occur in extremely athletic women with a long history of low body weight and extensive exercise. There is also a genetic possibility for this condition.
Although currently unexplained, "unruptured follicle syndrome" occurs in women who produce a normal follicle, with an egg inside of it, every month yet the follicle fails to rupture. The egg, therefore, remains inside the ovary and proper ovulation does not occur.
Causes of Poorly Functioning Fallopian Tubes
Tubal disease affects approximately 25% of infertile couples and varies widely, ranging from mild adhesions to complete tubal blockage. Treatment for tubal disease is most commonly surgery and, owing to the advances in microsurgery and lasers, success rates (defined as the number of women who become pregnant within one year of surgery) are as high as 30% overall, with certain procedures having success rates up to 65%. The main causes of tubal damage include:
Caused by both bacteria and viruses and usually transmitted sexually, these infections commonly cause inflammation resulting in scarring and damage. A specific example is Hydrosalpnix, a condition in which the fallopian tube is occluded at both ends and fluid collects in the tube.
The most common of these are appendicitis and colitis, causing inflammation of the abdominal cavity which can affect the fallopian tubes and lead to scarring and blockage.
This is an important cause of tubal disease and damage. Pelvic or abdominal surgery can result in adhesions that alter the tubes in such a way that eggs cannot travel through them.
This is a pregnancy that occurs in the tube itself and, even if carefully and, successfully overcome, may cause tubal damage and is a potentially life-threatening condition.
In rare cases, women may be born with tubal abnormalities, usually associated with uterus irregularities.
Approximately 10% of infertile couples are affected by endometriosis. Endometriosis affects five million US women, 6-7% of all females. In fact, 30-40% of patients with endometriosis are infertile. This is two to three times the rate of infertility in the general population. For women with endometriosis, the monthly fecundity (chance of getting pregnant) diminishes by 12 to 36%. This condition is characterized by excessive growth of the lining of the uterus, called the endometrium. Growth occurs not only in the uterus but also elsewhere in the abdomen, such as in the fallopian tubes, ovaries and the pelvic peritoneum. A positive diagnosis can only be made by diagnostic laparoscopy, a test that allows the physician to view the uterus, fallopian tubes, and pelvic cavity directly. The symptoms often associated with endometriosis include heavy, painful and long menstrual periods, urinary urgency, rectal bleeding and premenstrual spotting. Sometimes, however, there are no symptoms at all, owing to the fact that there is no correlation between the extent of the disease and the severity of the symptoms. The long term cumulative pregnancy rates are normal in patients with minimal endometriosis and normal anatomy. Current studies demonstrate that pregnancy rates are not improved by treating minimal endometriosis.