Causes of Female Infertility

1.  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. Fortunately, approximately 70% of these cases can be successfully treated by the use of drugs such as Clomiphene and Menogan/Repronex.  See more information on the causes of failed ovulation.

2.  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%. See the main causes of tubal damage.

3.  Endometriosis

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.

4.  Additional factors

1. Other variables that may cause infertility in women:
    
   • Abnormal uterus: At least 10% of all cases of female infertility are caused by an abnormal uterus. Conditions such as fibroid, polyps, and adenomyosis may lead to obstruction of the uterus and Fallopian tubes.
      
   • Congenital abnormalities: Congenital abnormalities such as septate uterus, may lead to recurrent miscarriages or the inability to conceive.
      
   • Cervical mucus: Approximately 3% of couples face infertility due to problems with the female's cervical mucus. The mucus needs to be of a certain consistency and available in adequate amounts for sperm to swim easily within it. The most common reason for abnormal cervical mucus is a hormone imbalance, namely too little estrogen or too much progesterone.  
   
   
2. Lifestyle factors

   It is well-known that certain personal habits and lifestyle factors impact health; many of these same factors may limit a couple's ability to conceive. Fortunately, many of these variables can be regulated to increase not only the chances of conceiving, but also one's overall health.
    

3. Environmental and occupational factors

   The ability to conceive may be affected by exposure to various toxins or chemicals in the workplace or the surrounding environment. Substances that can cause mutations, birth defects, abortions, infertility or sterility are called reproductive toxins.

5.  Unexplained infertility

Infertility is customarily defined as the inability to conceive after one year of regular unprotected intercourse. The infertility evaluation is typically initiated after 1 year of trying to conceive, but in couples with advanced female age (> 35 years), most practitioners initiate diagnostic evaluation after an inability to conceive for 6 months.

The Practice Committee of the American Society for Reproductive Medicine (ASRM) has published guidelines for a standard infertility evaluation. It includes a semen analysis, assessment of ovulation, a hysterosalpingogram, and, if indicated, tests for ovarian reserve and laparoscopy. When the results of a standard infertility evaluation are normal, practitioners assign a diagnosis of unexplained infertility.
 

Much of the above information is from the stanford.edu website.