Test Your Knowledge

There are many potential causes of infertility. Overall, about one-third of infertility cases can be attributed to males, another one-third to females and the remaining one-third to both members of a couple. At least 20 percent of infertility cases go unexplained, although these couples often later succeed in becoming pregnant.

Ovulation abnormalities in women and sperm deficiencies in men are responsible for two-thirds of infertility problems. When ovulation fails to occur, there is no egg available for fertilization. In some cases, this is a result of a breakdown in a woman’s hormonal communication cycle. This disruption takes place in the part of the brain that regulates ovulation, known as the hypothalamic pituitary axis. This can cause deficiencies in the production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Specific causes of this disorder include:

• Direct injury to the hypothalamus or pituitary gland
• Pituitary tumors
• Excessive exercise
• Anorexia nervosa

Ovulation problems may also occur when the ovaries no longer contain eggs to be fertilized, or scar tissue prevents ovulation from occurring. Signs of ovulation problems include irregular menstrual periods or the absence of menstruation (amenorrhea).

Smoking may contribute to infertility in men and women. In women, smoking is harmful to the ovaries, and in men smoking lowers sperm count and impairs sperm motility.

Difficulties with a man’s sperm can also cause infertility. Most cases of male infertility are associated with:

• Low sperm production (oligospermia).
  
  
• Lack of sperm (azoospermia).
  
  
• Poor sperm motility. Sperm may not move properly inside the female reproductive tract (poor motility) or may be malformed or die before reaching the egg.
  
  
• Variocele veins. Varicose veins in the scrotum that may prevent normal cooling of the testicles and raise temperature, preventing sperm from surviving.
  
  
• Undescended testicle. Occurs during development and may cause mild to severely impaired sperm production.
  
  
• Testosterone deficiency. May be caused by testicular disorders or an abnormality that affects the pituitary gland in the brain that produce the hormones and control the testicles.
  
  
• Infection. Infection may affect sperm motility. Repeated incidents of sexually transmitted diseases (STDs) can cause scarring and block sperm passage, and are most often associated with male infertility. A mumps infection after puberty may cause inflammation of the testicles that can impair sperm.
  
  
• General health and lifestyle. Lifestyle factors that can affect fertility include obesity, emotional stress, tobacco and alcohol use, drug use, other medical conditions, and age over 35 years.

Factors that impair the delivery of sperm from the penis to the vagina can also cause infertility (e.g., erectile dysfunction, misplaced urinary opening in the penis with sometimes retrograde ejaculation).

There are many different sources of female infertility. The most common include:

• Fallopian tube damage or blockage. Most often results from inflammation of a fallopian tube, a condition known as salpingitis. The STD chlamydia is the most common source of this disorder, which may cause pain or fever, but sometimes does not cause symptoms. About 20 percent of infertility cases are the result of fallopian tube damage, according to the National Women’s Health Resource Center. Symptoms include pelvic pain, unusual vaginal discharge, bleeding and fever.
  
  
• Endometriosis. Occurs when the tissue that makes up the lining of the uterus is found outside the uterus on the ovaries, fallopian tubes, bladder or bowel. Symptoms include painful menstrual cramps, very heavy menstrual flow, diarrhea or painful bowel movements, painful sexual intercourse and chronic pelvic pain. Between 30 and 40 percent of women with endometriosis are infertile, according to the National Institutes of Health. Infertility increases with the severity of the disease. The fertility of women with mild disease may not be compromised. In some cases, infertility in endometriosis is due to:
  
  
• Ovarian cysts (endometriomas). These may indicate advanced endometriosis. The cysts can usually be removed with surgery.
  
  
• Scar tissue. In some cases, endometriosis causes rigid webs of scar tissue (adhesions) between the uterus, ovaries and fallopian tubes. This may prohibit the transfer of the egg to the fallopian tube. It is the presence of significant adhesions that can impair fertility in women with endometriosis.
  
  
• Hormonal imbalances. The normal variation in the length of the menstrual cycle in women may cause difficulties in determining the time of ovulation. Some imbalances may cause unpredictable cycles. In addition, elevated levels of the hormone prolactin (hyperprolactinemia) – which may indicate a pituitary tumor – may affect ovulation in women who are not breastfeeding.
  
  
• Polycystic ovarian syndrome (PCOS). A type of reproductive disorder in which excessive amounts of androgens (male hormones such as testosterone) are produced by the ovaries. This may prevent the follicles of the ovaries from producing a mature egg.
  
  
• Sexually transmitted diseases. Left untreated, some STDs can lead to pelvic inflammatory disease (PID), and infection of the upper genital tract that may hamper fertility. Other complications include scarring, adhesions, blocked fallopian tubes, ectopic pregnancy and miscarriage. The STDs chlamydia and gonorrhea are the most important preventable causes of infertility, according to the U.S. Centers for Disease Control and Prevention.
  
  
• Early menopause. This is defined as the absence of menstruation and the depletion of ovarian follicles before age 35. The cause is often unknown, but may include autoimmune disease, radiation or chemotherapy, or smoking.
  
  
• Uterine fibroids. These small noncancerous (benign) tumors of the uterine wall may block the fallopian tubes as well as affect the lining of the uterus which may prevent implantation.
  
  
• Pelvic adhesions. Bands of scar tissue that bind organs after pelvic infection, appendicitis, and abdominal or pelvic surgery. They may limit the ability of the ovaries and fallopian tubes to function.
  
  
• Thyroid problems. Disorders of the thyroid gland can disrupt the menstrual cycle and trigger infertility.
  
  
• Cancer. Certain cancers – particularly gynecological cancers – can impair fertility. In addition, cancer treatments such as radiation and chemotherapy may affect a woman’s ability to conceive.
  
  
• Maternal exposure to DES. Diethylstilbestrol (DES) is a synthetic estrogen that was developed in 1938 to supplement natural estrogen production. Women who were exposed to DES in the womb, known as DES daughters, are at an increased risk of gynecological problems, including infertility.
  
  
• Diseases associated with amenorrhea (absence of menstruation) or delayed puberty. These include Cushing’s disease, sickle cell disease, HIV and AIDS, kidney disease and diabetes. In addition, girls who have eating disorders such as anorexia and bulimia often develop menstruation irregularities that can lead to infertility.
  
  
• Multiple miscarriages. Two or more losses of pregnancy can lower the odds of further pregnancies.
  
  
• Being overweight. Infertility can result from a sedentary lifestyle and being overweight or obese. These issues can affect many aspects in the process including ovulation.

In addition to irregularities, aging can also reduce a woman’s fertility. After age 35, a woman’s fertility rapidly declines as her ovaries produce fewer viable eggs. Egg quality is a major factor in whether a woman becomes pregnant. Women can increase their odds of becoming pregnant by trying to conceive earlier in life. Most women are about 30 percent less fertile in their late 30s than they were in their early 20s, according to the National Women’s Health Resource Center.

Women who take birth control pills over many years do not become infertile. Once they stop taking the pill, they can become pregnant, although initially there may be lingering effects from the last use that could prevent conception. This lag period can last for up to three months after the last use.