|Causes of Infertility|
There are many different causes of infertility. There are also different methods for categorizing the causes of infertility. The prevalence of each of the causes of infertility will vary substantially depending on the population being studied. Some of the more common causes of infertility are discussed below.
Female infertility causes
One of the most basic requirements for a pregnancy is that a mature healthy egg must be present in the fallopian tube for a sperm to fertilize. Normally, a woman will mature a single egg and release that egg into the fallopian tube once a month. Infertility can result if a woman does not mature or release eggs on a regular basis. Some women may have problems that cause them to ovulate sporadically while other may never ovulate on the own without help.
Testing can be performed on women with ovulation problems. Testing will be able to find a cause for ovulation problems is a large number of cases and very often the cause of the underlying ovulation problem can be treated and result in regular ovulation and pregnancy.
Signs of an ovulation problem include the failure to get periods, infrequent or irregular periods.
As women age, their ability to become pregnant decreases. The reason for this problem is that women have all of the eggs they are ever going to have in their lives before they are born. All during their lives, the number of eggs decreases because of ongoing degeneration. The fewer the number of eggs that remain, the poorer the "quality" of those eggs and the harder it is to get pregnant.
Besides age, factors that accelerate the decrease in the number of eggs may also cause infertility. For example, cigarette smoking, endometriosis , ovarian surgery and immune problems may all result in the destruction of eggs.
The most severe symptom of poor ovarian reserve is the complete failure of the ovaries with resulting lack of periods. This is a problem known as primary ovarian insufficiency or premature ovarian failure .
Unfortunately, there are no successful treatment for decreased ovarian reserve. All fertility treatments except for egg donation will result in a low chance for success.
Anatomic causes of infertility
Blocked fallopian tubes
In order for pregnancy to occur, the egg must be fertilized by a sperm in the fallopian tube and the resulting embryo must travel into the uterus and implant in the uterine lining. Blockage of the fallopian tubes will prevent the sperm from meeting the egg and/or prevent the egg from entering the fallopian tube.
Fallopian tube blockage can be diagnosed with an x-ray test known as a hysterosalpingogram or HSG . In many cases, fallopian tube blockage can be corrected at the time of an HSG using techniques such as selective salpingography or wire guide canalization . In some cases, surgery can be performed to unblock a fallopian tube.
The uterine cavity normally has a triangular shape. Some women are born with abnormalities of the uterus. These abnormalities are a less common cause of infertility. Uterine cavity abnormalities can be diagnosed by hysterosalpingogram , saline ultrasound , hysteroscopy or MRI. Most types can be fixed with surgery.
Commonly, growths can occur in the uterus with can distort the shape of the uterine cavity. The most common growths are called polyps or fibroids . These growths can also be detected by hysterosalpingogram, ultrasound, saline ultrasound, hysteroscopy or MRI. Most can be treated with surgery.
Contrary to common belief, the ovary is not attached to the opening of the fallopian tube. A complicated process causes the ovary to become sticky at the point where the egg is going to be released. The fallopian tube must temporarily adhere to this spot to allow the egg to enter the tube. If the opening of the tube is blocked, this will not occur.
Scar tissue involving the tubes and/or ovaries, also called pelvic adhesions, can decrease the likelihood that an egg will enter the fallopian tube and therefore be a cause of infertility. Pelvic adhesions can usually be detected only though exploratory issue. Only in rare cases will a physician be able to detect scar tissue via ultrasound or other conservative method.
Scar tissue can result from pelvic infections, endometriosis , previous surgical procedures or anything that causes inflammation in the abdomen such as appendicitis.
Scar tissue can be removed with surgery and normal pelvic anatomy restored, but it can recur.
Endometriosis is a condition in which the tissue that normally grows inside the uterine cavity, grows outside the uterus. Endometriosis has been cited as a common cause of infertility. Symptoms of endometriosis can range from no symptoms at all, infertility, pelvic pain or a combination of pain and infertility. Endometriosis is graded by the extent of abnormal tissue that is present. The common endometriosis scoring method goes from minimal, mild, and moderate to severe.
Milder forms of endometriosis cannot be detected without exploratory surgery. More severe versions will often cause cysts to form in the ovaries known as endometriomas. These endometriomas can be detected with ultrasound.
Endometriosis can be treated surgically, with medication or with other types of fertility treatments such as IVF.
Abnormal cervical mucous
Normally, mucus in the cervix (the lower part of the uterus that opens into the vagina) is thick and impenetrable to sperm until just before release of an egg (ovulation). As the egg develops in the ovary, estrogen is produced. The estrogen will gradually change the mucus so that it be comes clear and watery. As a result, sperm can move through the mucus into the uterus more easily. If the mucus does not change at ovulation (usually because of an active infection), pregnancy is unlikely.
A woman may be able to detect he changes in her cervical mucus. In the past, physician would perform a test after a couple has intercourse to observe if sperm were able to move freely within the mucus. This test, called a post-coital test, has been abandoned by competent fertility doctors because of an abundance of evidence that it was not predictive of whether couples would be able to achieve pregnancy.
Hormone imbalances usually cause infertility be interfering with ovulation. However, there may be cases in which ovulation still occurs but pregnancy is less likely to occur. For example, women who have thyroid gland abnormalities (either underactive or over active) have a higher rate of infertility.
Some women produce excess amounts of prolactin, a hormone that normally stimulates the production of breast milk. Prolactin can also prevent ovulation. Prolactin elevations may cause deficient production of progesterone from the ovaries after ovulation, this is known as a luteal phase defect.
Obesity is perhaps the most common cause of infertility in the United States today. Obesity is defined as a body mass index over 30. Infertility is much more common in obese women compared to thinner women. Once study found that every body mass index point over 30, there is a four percent lower chance of a couple getting pregnant on their own. So a woman with a BMI of 40, would have a 40% lower chance for becoming pregnant.
Obesity has also associated with a lower chance for successful fertility treatment. When pregnancy does occur in obese women, there is an increase the chance that pregnancy will be lost from miscarriage. Obese women also have a higher rate of tubal (ectopic) pregnancies and other complication.
It is well known that when a man ejaculates, millions of sperm are released. The sperm must swim through the female reproductive tract into the fallopian tube in order to fertilize the egg.
Men who make small amounts of sperm or that have a smaller percentage of sperm that swim well will have more difficulty producing a pregnancy in their partner. In addition, men with a high percentage of sperm with an abnormal shape, also have a higher chance of infertility.
In some cases, examination of a male may reveal the cause for sperm problems. In some of these cases, it may be possible to directly treat a male in order to improve the sperm numbers. In other cases, the fertility doctor can make better use of sperm with techniques such as intrauterine insemination (IUI) or in vitro fertilization (IVF)
|Last Updated ( Tuesday, 24 November 2009 )|