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What are the Main Causes of Infertility?
The main causes of infertility include:
- Male Factor Infertility
- Ovulation disorders
- Disorders of the fallopian tubes and/or uterus
- Endometriosis
- Weight and Fertility
- Age and Decreased Ovarian Reserve
- Unexplained Infertility
Male Factor Infertility
Though the cause of male infertility is often unidentified, there are a few problems that have been indicated as potential causes. Problems related to sperm production, the anatomy or structure of the man's reproductive organs and the man's immune system can all be factors in male infertility.
Genetic defects, infection, testicular trauma, hormonal imbalance or exposure to radiation and certain medications are all causes of sperm production disorders. Infertility can occur when there is a low sperm count, or problems with the motility (movement) or morphology (appearance or shape) of the sperm. Sperm that have poor motility often are not able to reach the egg and, therefore, fertilization does not occur. Abnormal sperm are sometimes unable to penetrate and fertilize the egg. Sperm DNA damage may interfere with conception as well as lead to a greater risk of miscarriage. Any structural or anatomical problems that block the path that sperm must travel to eventually reach the egg for fertilization can cause male infertility. Infertility related to structural and anatomical problems in the male anatomy may be caused by scar tissue, varicose veins or infection or, in some cases, the problems exist from birth.
In some cases, men have immune system disorders which cause their bodies to develop antibodies to their own sperm, which attack and weaken the sperm. The antibodies can also attach to the sperm surface and interfere with their movement or ability to fertilize the egg.
Ovulation Disorders
Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women, affecting an estimated five to ten million women of reproductive age. For women trying to conceive a child, PCOS is a serious, common cause of infertility - nearly half of all female factor infertility cases can be traced to PCOS. New medical insight into the disease has led to treatment options, including insulin-reducing medication (Glucophage®), dietary changes (low glycemic diet) and surgery (ovarian drilling). These have proven successful and allow many women to overcome PCOS and conceive a child naturally, while reducing the risk of miscarriage. Women who undergo treatment for PCOS but are still unable to conceive naturally often turn to assisted reproductive technologies, including IVF, and experience high pregnancy success rates.
| Research Highlight: Too Much Exercise May Be Bad for Fertility A study concludes that overly frequent and hard physical exercise appears to reduce a young woman's fertility. The Norwegian University of Science and Technology 12 November 2009 |
Additonally, female athletes or those who are involved in very heavy exercise often experience ovulation problems and may need to resolve these issues before receiving specific treatment for infertility.
Disorders of the Fallopian Tubes and/or Uterus
One of the causes of infertility is fallopian tube disease in which your fallopian tubes become blocked or damaged. Scar tissue resulting from endometriosis or abdominal or gynecological surgery (bowel surgery, cesarean section, ruptured appendix, etc) can block the sperm. Infections, such as Chlamydia, can damage the cilia (tiny hairs lining the fallopian tubes) that help to transport the egg. Without normal cilia, the egg may not meet the sperm, or if an egg becomes fertilized, it may not be able to travel to the uterus. This can result in an ectopic pregnancy, which can further damage your tube. Adhesions (scar tissue) can form inside of the pelvis - inside or around the ends of the fallopian tubes and block an egg and sperm from meeting. Adhesions that develop on the ovaries may disrupt ovulation and those that develop inside the uterus may prevent a fertilized egg from implanting properly. A woman can also have an unusually shaped uterus that prevents successful implantation also.
Endometriosis
Endometriosis, a cause of female infertility, is a condition in which endometrial tissue, the tissue that lines the inside of the uterus, grows outside the uterus and attaches to other organs in the abdominal cavity such as the ovaries and fallopian tubes. Endometriosis is a progressive disease that tends to get worse over time and can reoccur after treatment. Symptoms include painful menstrual periods, abnormal menstrual bleeding and pain during or after sexual intercourse.
The endometrial tissue outside your uterus responds to your menstrual cycle hormones the same way the tissue inside your uterus responds - it swells and thickens, then sheds to mark the beginning of the next cycle. The blood that is shed from the endometrial tissue in your abdominal cavity has no place to go, resulting in pools of blood causing an inflammation that forms scar tissue. The scar tissue can block the fallopian tubes or interfere with ovulation. Another result of endometriosis is the formation of ovarian cysts called endometriomas that may also interfere with ovulation.
The cause of endometriosis is unknown though there are a few theories that suggest possible causes. One theory suggests that during menstruation, some of the menstrual tissue backs up through the fallopian tubes into the abdomen where it implants and grows. Another theory indicates that it is a genetic birth abnormality in which endometrial cells develop outside the uterus during fetal development.
A laparoscopy, an outpatient surgical procedure, is necessary to confirm a diagnosis of endometriosis after a medical history review and pelvic exam. After the initial diagnosis, your physician will classify your condition as stage 1 (minimal), stage 2 (mild), stage 3 (moderate) or stage 4 (extensive) based on the amount of scarring and diseased tissue found. Based on the stage of endometriosis, your physician will determine the best treatment plan for you which may include medication or surgery, or a combination of both.
Weight and Fertility
Being overweight or obese may reduce a woman's fertility due to irregular or infrequent menstrual cycles. Obesity may also cause an increased risk of miscarriage and decreased success with fertility treatments. When pregnancy is achieved, women with excessive weight increase their risks associated with pregnancy, such as high blood pressure, gestational diabetes, birth defects, high birth-weight infants and an increased risk of Cesarean section. Weight loss may improve fertility and pregnancy outcome. A body mass index (BMI) of 25 to 29.9 is considered overweight, and obesity is defined as a BMI of 30 and above. Weight loss of 5% to 10% may dramatically improve ovulation and pregnancy rates. See Patient's Fact Sheet: Weight and Infertility to determine your ideal BMI based upon your height and weight.
Age and Decreased Ovarian Reserve
As a woman ages, her fertility decreases. This decrease usually occurs slowly up until about 35 years of age, when fertility falls even faster. This drop in fertility is seen even in women who have perfectly normal, regular menstrual cycles. In fact for some women, fertility may no longer be possible five to 10 years before menopause. Diminished fertility, also called diminished ovarian reserve, is thought to reflect both a decreased number of eggs and a decrease in egg quality.
Unexplained Infertility - "What if all of the tests are normal?"
In some couples, no obvious cause for their infertility is found. This is called unexplained infertility and may occur in 15-20% percent or less of couples after the work-up and evaluation are completed. Unexplained infertility simply means that we do not know why the couple is not fertile. People with unexplained infertility do have a cause for their infertility, but due to limitations of our current testing, we cannot determine the reason.
The diagnosis is one of exclusion-that is, one that is made only after all the tests have been performed and their results found to be normal. Infertility may be labeled as "unexplained" when:
- the woman is ovulating regularly, has open fallopian tubes with no evidence of adhesions or endometriosis;
- the man has normal sperm production;
- sexual intercourse takes place frequently, particularly around the time of ovulation; and,
- the couple has been trying to conceive for at least one year
Because unexplained infertility carries no specific diagnosis, the treatment recommended by fertility specialists is empiric. This means that the treatment is done to optimize a couple's chance of successful conception but is not used to treat or overcome a specific problem. Sometimes the diagnosis is simply not as straightforward or easy to diagnose. Instead of spending valuable time on testing, it is more efficient to treat subtle defects with of ovulation or sperm function with medication combined with artificial inseminations.
In some instances, couples with unexplained infertility will conceive over time with no treatment. In fact, fifty percent of couples diagnosed with unexplained infertility, who have never had a child before, will conceive within five-and-a-half years. For those couples wishing to expedite this process and not simply wait, there are proven methods to increase the chance of pregnancy even when no specific diagnosis can be made. For more information on unexplained infertility see Patient's Fact Sheet: Unexplained Infertility.