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Causes of Female Infertility

Infertility is generally defined as one year of unprotected intercourse that does not result in the conception of a child. The most common causes of reduced fertility in women include:

Advancing Age
Amenorrhea
Endometriosis
Ovulatory Disorders
Polycystic Ovarian Syndrome
Recurrent Pregnancy Loss
Unexplained Infertility
Tubal Factor Infertility

Advancing Age

As women age, their fertility declines. For most women, this begins slowly in their late 20's and the decline is much steeper by 37 - 38. It is actually quite rare for women in their late 40's and 50's to conceive a child without assistance as aging eggs do not fertilize, implant or respond to stimulation medications as well as younger eggs. Such eggs also present an increased risk of miscarriage and babies with Down's syndrome and other chromosomal abnormalities.

Amenorrhea

Amenorrhea is simply the absence of periods. There are two types of amenorrhea: primary and secondary. Primary can occur when a woman does not have any menstrual periods before the age of 16. Secondary amenorrhea can occur when a woman has previously menstruated but then stops having periods for 3-6 months or more. There are many reasons, both hormonal and physical, why you might stop having your period.

Endometriosis

Endometriosis is a common disorder that affects women during their reproductive years. It occurs when endometrial tissue, which lines the uterus, grows outside the uterine cavity. This misplaced tissue may implant and grow anywhere within the abdominal cavity in locations such as the ovaries and fallopian tubes.

Endometriosis is unpredictable. Some women have a few implants which never spread or grow; in other women, the disease may spread throughout the pelvis. Many women experience no symptoms; others have severe menstrual cramps, abnormal uterine bleeding, painful intercourse and other symptoms. Minimal endometriosis may cause severe pain, while extensive endometriosis may cause no discomfort.

Some women with endometriosis are able to conceive, while others may not. It can hinder conception by producing scar tissue or adhesions which bind the ovaries, fallopian tubes and intestines together. These adhesions can interfere with the release of eggs from the ovaries or the pick-up of eggs by the fallopian tube. This reduces the chance of pregnancy. The causes of endometriosis are not fully understood but several theories exist including genetic factors, subtle changes in the immune system, and retrograde menstruation in which the menstrual discharge flows backwards through the fallopian tubes into the pelvis.

Diagnosis cannot be made from symptoms alone. The doctor may suspect endometriosis based on history and the results of a pelvic exam, but additional studies are required to confirm it. A laparoscopy is often the only valid diagnostic tool, enabling the doctor to see the endometriosis and gauge its extent. The patency of the tubes can also be checked at this time by injecting dye into the uterus and through the tubes. Other diagnostic tools include ultrasound and blood tests.

Ovulatory Disorders

Producing a fertilizable egg each month requires a series of intricate interactions between the hormones produced in your brain and ovaries. If one thing is off, out of sync or missing in this interaction, you won't be able to get pregnant. A number of conditions can interfere with or even prevent ovulation including:

Polycystic Ovarian Syndrome
Thyroid disease
Hyperprolactinemia, a hormone that stimulates milk production and suppresses ovulation
Low levels of the fertility hormones (FSH and LH)
Premature Ovarian Failure
Extreme weight loss or weight gain
Excessive exercise
Eating disorders

Ovarian dysfunction occurs when there is a decline in both egg quantity and quality making it difficult for a woman to conceive. Some women experience this long before they reach menopause. Known as Premature Ovarian Failure (POF), or early menopause, it occurs when a woman under the age of 40 stops producing eggs capable of fertilization. On average, the age for natural menopause is about 51, but women with POF go into menopause much sooner.

Anovulation may also be caused by an elevation of the pituitary hormone, prolactin. Hyperprolactinemia, is an abnormal elevated prolactin level in the non-pregnant woman. High levels of prolactin lead to irregular ovulation and are often caused by a small tumor on the pituarity gland. This can be treated with medication or surgery. Ovulation and conception can be achieved in a significant number of these women.

Ovulatory disorders are the most common cause of female infertility and many of these problems are treatable.

Polycystic Ovarian Syndrome

Polycystic ovary syndrome (PCOS), or polycystic ovary disease (PCOD), is an endocrine disorder and one of the most common hormone problems of reproductive-aged women. Despite the name, there are not usually cysts on the ovaries, although some women have many small follicles visible on ultrasound. The hormone imbalance interferes with the cyclical production of eggs. Some women with PCOS experience irregular ovulation, often having less than eight menstrual cycles per year. Other women with PCOS can have more than one period of bleeding per month and each episode can be lengthy.

PCOS is sometimes associated with a resistance to insulin. Elevated insulin levels stimulate the ovaries to produce androgens (male hormone). Women with PCOS are also at increased risk for diabetes, heart disease and high cholesterol. Proper diet and exercise are very important in managing this problem.

Recurrent Pregnancy Loss

A miscarriage is the loss of a pregnancy before 20 weeks gestation. It occurs in 15 - 20 percent of pregnancies and the risk increases with age. Most miscarriages, also known as spontaneous abortions or pregnancy losses, occur within the first trimester. If a viable fetus (heart activity is seen by ultrasound) is detected in the first 12 weeks of gestation, there is a less than five percent chance of pregnancy loss. If vaginal bleeding occurs after a viable fetus is detected, the chance of miscarriage increases to about 20 percent.

The chances of having recurrent pregnancy loss vary widely. Women who have had at least one full-term normal delivery have a better chance of a subsequent healthy pregnancy, despite having a miscarriage. Extensive evaluation usually occurs only after at least two or three consecutive miscarriages. A cause for recurrent pregnancy loss will be identified in about half of the couples and treatment can often resolve the problem. Most miscarriages are due to an abnormal chromosome pattern in the embryo and are unrelated to the health of the mother although the risk of miscarriage increases for women 35 years of age and older. By age 40, the risk is 35 - 40% and by 45 years of age it is greater than 50%.

Recurrent pregnancy loss may be due to some of the following factors:

Abnormalities in the Shape of the Uterus
Uterine Fibroids
Genetic Abnormalities
Hormonal Disorders
Immunological Factors
Infection
Unexplained

Causes of Recurrent Pregnancy Loss (RPL)

Recurrent pregnancy loss is defined as three consecutive pregnancy losses (miscarriages). Some of the following factors may be involved:

  • Abnormalities in the Shape of the Uterus
    Approximately 10 to 15 percent of women with a history of RPL have an abnormally shaped uterus. One example is a septate uterus, which is a uterus with a dividing wall of tissue (septum) within the uterine cavity. This congenital abnormality occurs in about one in every three hundred women and 80 percent of these women have reproductive difficulty. After spetum repair 80 percent of women with RPL have a successful pregnancy.

  • Uterine Fibroids
    One of every four to five women have uterine fibroids. Fibroids are benign masses of smooth muscle tissue in and around the uterine wall. They are usually harmless but they can cause excessive uterine bleeding, pain, miscarriages and infertility. Fibroids may cause changes in the endometrium or in the blood supply to the uterus which can lead to miscarriage, increased risk of premature delivery and other problems. Uterine fibroids can usually be diagnosed during a pelvic examination. Diagnostic procedures include ultrasound, hysterosalpingogram (an x-ray image of the inside of the uterus and fallopian tubes), diagnostic laparoscopy and hysteroscopy. In most cases, fibroids do not require treatment. Periodic examinations will determine if they are growing. They can be treated medically with hormones. Surgical removal should be considered only if they are causing significant symptoms or are growing rapidly.

  • Genetic Abnormalities
    The major cause of an early miscarriage is probably a genetic factor. Over 50 percent of first trimester miscarriages show evidence of genetic defects. The most common defect is an abnormal number or structure of chromosomes, which is a normal natural event occurring by chance. Chromosomes are located in the nucleus (center) of cells and contain the genes, the basic units of inherited characteristics. In cases where genetic abnormalities will lead to continued pregnancy losses, the couple should discuss treatment options with their physician. About 5% of recurrent pregnancy loss is due to a chromosome problem in one of the parents.

  • Hormonal Disorders
    In the second half of the menstrual cycle, the hormone progesterone, produced by the ovaries, causes the endometrium to thicken and become a healthy environment for the embryo. If progesterone production is low, miscarriage can result because the embryo cannot become implanted securely. A microscopic examination of tissue from the uterine lining can diagnose this condition. It is treated with hormones. Disorders of the thyroid gland, such as over activity (hyperthyroidism) or under activity (hypothyroidism), are linked to miscarriage. These disorders are diagnosed with a blood test and can be treated with medication.

  • Immunological Factors
    The immune system plays a role in maintaining health and responding to infection, injury or introduction of foreign material. The role of the immunologic interaction between mother and fetus is not fully understood but seems to fall into two categories:
    • The pregnant woman's body produces certain immunoglobulins that are directed against circulating substances that affect blood clotting. These antibodies can affect fetal development, resulting in miscarriage.
    • During a normal pregnancy, the fetus, which carries the father's foreign genes, survives in the mother's uterus because of a special protective response from her immune system. If this protective response does not occur, the maternal immune system rejects the father's foreign material in the fetus, resulting in miscarriage. How much role the immune system plays, if at all, is unknown and controversial.
  • Infection
    Infections may cause recurrent pregnancy loss but studies fail to indicate a greater incidence of infection in women with a history of recurrent miscarriages when compared to normal fertile women. When evaluating a couple with a history of repeated early pregnancy loss, some physicians will take cultures to check for infectious organisms. If an infection is identified, antibiotics are usually prescribed for both partners and a re-culture is done. There is no definite proof that antibiotic treatment will increase the chances of a normal pregnancy.

  • Unexplained
    Knowledge of miscarriage is still limited. No obvious cause is detected in up to 50 percent of couples with repeated pregnancy losses. When the causative factor can be diagnosed and treated, the success rate is high, especially with certain uterine and hormonal causes. In cases where no cause is discovered and no treatment prescribed, the chance of achieving a healthy pregnancy, despite having had several miscarriages, is still generally better than 50 percent.

Unexplained Infertility

If a cause for infertility is identified, the physician may suggest a specific treatment. However, sometimes no specific problem is identified and the infertility is unexplained.

Unexplained infertility is defined as more than three years of infertility with normal semen analysis, normal ovulation by basal body temperature charting or serum progesterone and normal tubes and pelvic cavity on laparoscopy, with or without a hysterosalpingogram (HSG). Other tests such as postcoital test, antibody (immune), and endometrial biopsies are no longer performed as the results do not prove helpful for therapy. Patients with normal studies and less than three years infertility have a 60 percent chance of conceiving within 18 months without therapy. After three years, however, the chances are 30 percent or less of ever conceiving depending on the age of the woman and length of infertility. This is equivalent to about three percent per month or less. So called "fertility" pills are not helpful for this group; recent studies suggest they may actually lower fertility in ovulating women.

With unexplained infertility or when traditional treatments have failed, advanced infertility therapies may be suggested. These include HS/IUI and IVF/ICSI.

Tubal Factor Infertility

The fallopian tubes play an important role in fertilization and pregnancy. Damaged tubes are the cause of infertility in as many as 25 percent of infertile women. The good news is that many women with tubal damage can achieve pregnancy using modern techniques.

The fallopian tubes are two hollow structures, each connected to one side of the uterus and each extending to the surface of an ovary. The ovary end of each tube is flared open with "fingers" (fimbriae) that sweep over the ovary's surface and direct the released egg into the tube. The tube lining provides nutrition to the egg and is where fertilization occurs.

Damage to the fimbriae may reduce or eliminate their ability to pick up the egg and direct it into the tube. Damage to the cells of the lining may prevent or reduce the chance of fertilization. Blockage in the tube can prevent the fertilized egg from moving to the uterus, thereby increasing the incidence of ectopic pregnancy.

Tubal damage can result from tubal ligation (sterilization), tubal infection or scarring. Pelvic infection is caused by appendicitis, bowel infection, douching or sexually transmitted diseases such as Gonorrhea, Chlamydia and Tuberculosis.

There are two types of tubal blockage: proximal (close to the uterus) and distal (away from the uterus). Proximal blockage can be caused by previous pelvic infection, mucus plugs, thickening and inflammation of the tubal wall, or endometriosis. Distal blockage is generally caused by pelvic inflammation, which may be secondary to infection or endometriosis. Pelvic infection is caused by appendicitis, bowel infection, douching or sexually transmitted diseases. Many women do not know they have had a pelvic infection serious enough to damage the tubes until they attempt pregnancy and fail to conceive.

Scar tissue or adhesions around the tube and ovary can occur in women who have never had a pelvic infection. Previous tubal surgery or other abdominal surgery can result in tubal problems and pelvic scarring, especially if the surgery was extensive or involved a severe infection. Any distortion or constriction of the tube can prevent an egg and sperm from meeting or can increase the likelihood of a tubal pregnancy.

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