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Infertility occurs when a couple has been having regular sexual intercourse without any birth control for one year and the woman hasn't become pregnant. Ten to 20 percent of American couples experience infertility. Approximately half of these patients seek help and many will conceive with the appropriate treatment.

Most people affected by infertility are not irreversibly sterile; there is usually something that can be done to improve the chances of pregnancy. For some people, the treatment is as simple as learning to time intercourse around the woman's fertile period; others may have success with in vitro fertilization (IVF), in which the egg and sperm are united in the lab. Sperm and egg donors are available to partners who are unable to conceive using their own sperm or eggs.

The most common cause of infertility is the woman's age. Many women do not realize that their ovaries continue to age even if they are healthy and fit otherwise. While reports of women getting pregnant in their late 40s are common, many of these pregnancies come from donor eggs.

Infertility can be a major emotional burden. There are few conditions that have such a strong impact on one's daily life. The sense of family, connection with friends, financial security, spiritual grounding, and self-esteem can all be affected.

This section has more information on:

  • Need-to-know anatomy
  • Causes
  • Risk factors
  • Need-to-know anatomy

    The pituitary gland, located at the base of the brain, makes hormones that stimulate the reproductive organs. In men, the pituitary hormones tell the testicle to produce sperm and testosterone. Sperm moves from the testicle into the epididymis, which sits on top of the testicle and is like a bridge between the testicle and the vas deferens, the tube that carries sperm to the penis. The sperm matures in the epididymis, which has very high levels of testosterone. As it matures, it gains the ability to penetrate the egg and gains motility. Then the sperm moves into the vas and is ejaculated from there in a liquid called semen.

    In women, the pituitary gland releases hormones, including follicle-stimulating hormone (FSH) and luteinizing hormone (LH), that control the monthly reproductive cycle and stimulate the ovary to make estrogen and progesterone. Egg development begins before women are even born, and baby girls are born with about 2 million eggs in their ovaries—all the eggs they will ever make. Eggs are enclosed in follicles in the ovaries. Every month, hundreds of those follicles are destined to either ovulate or die. Only one egg, or sometimes two, is released per month. From the ovaries, the egg travels to the fallopian tubes, into the uterus, and is shed during menstruation if it is not fertilized.

    If you have intercourse around the time of ovulation—a woman's most fertile time is two or three days before ovulation—the sperm will have time to swim through the cervix, the uterus, the fallopian tubes, and be in the vicinity of the ovaries at the time of ovulation. A sperm fertilizes the egg near the ovaries, sometimes just inside the fallopian tubes. This usually happens within a day of ovulation, and then the fertilized egg travels through the fallopian tube and implants in the uterus about five days later.


    Infertility is not a simple disorder with one cause. For a pregnancy to occur, a long series of events must happen—and in the right order. Disruption in any of these processes can lead to infertility. The female must produce a healthy, mature egg and the ovary must release it. After release, the egg must travel toward the fallopian tube so it may be fertilized by the sperm. The male must produce a sufficient number of normal sperm that must be released from the penis and enter the vagina at the appropriate time during the menstrual cycle. It is only during this fertile time that the cervical mucus allows sperm to ascend through the cervix and into the uterus. Finally, the fertilized egg must travel to the uterus and implant in the endometrium (the uterine lining), which will nourish its further development.

    In some cases, couples who are unable to conceive simply aren't having intercourse often enough or aren't having intercourse during the woman's fertile time.

    The most common reason for infertility overall is the woman's age. Fertility generally starts to decline in the late 20s, with a more dramatic decline from the late 30s. Other factors that can contribute to female infertility include ovulation disorders such as polycystic ovarian syndrome (which involves high levels of male hormones and irregular or no menstruation), endometriosis (in which uterine lining tissue grows in places where it doesn't belong), and additional problems with the uterus or other reproductive structures. Diseases of the pituitary or hypothalamus glands can also interfere with the production of hormones. Stress, poor diet, smoking, and alcohol can also contribute to infertility. Some overweight women with infertility will find they are able to get pregnant after they lose weight. This is particularly true for women with polycystic ovarian syndrome.

    The most common male cause for infertility is a varicocele, a varicose vein in the scrotum.

    Although doctors understand many causes of infertility, there are still cases in which both partners seem to be perfectly healthy and fertile but are unable to conceive.

    This section contains more about:

    • Age
    • Ovulation disorders
    • Egg quality disorders
    • Blocked fallopian tubes
    • Endometriosis
    • Uterine anomalies
    • Varicocele
    • Steroids
    • Testicular problems
    • Chemotherapy and radiation therapy
    • Age

      The woman's age is the most common reason for infertility. Fertility doesn't necessarily correlate with overall health; a woman in her 40s can feel perfectly healthy and fit and still not be able to get pregnant. Female fertility starts to decrease slightly by age 28. However, in the late 30s, the drop in fertility becomes more pronounced. Up to 30 percent of 38-year-old women can no longer conceive their own genetic offspring. After age 43, the likelihood of pregnancy for a woman is very low. Although some women do have babies in their 40s and 50s, many of them have used donor eggs.

      Women have about 400,000 eggs in their ovaries by the time they start having menstrual bleeding. By age 38, the ovary still contains about 25,000 eggs. However, as eggs age, they are more likely be genetically abnormal. The body selects the healthiest eggs to grow and ovulate when a women is younger. So a 40-year-old will have a higher proportion of abnormal eggs than a 30-year-old. This affects whether a woman can get pregnant and also how well she will respond to fertility treatments.

      The 40s are the beginning of the slow transition to menopause. Women can't get pregnant after they go through menopause, which usually happens in their early 50s. But the change to menopause is not instantaneous—you aren't fertile one month and menopausal the next. Fertility is actually much lower the 10 years before menopause. Fertility can even start to decrease 15 to 20 years before menopause.

      In addition, many reproductive disorders become more common as women age. Older women are more likely to have endometriosis or problems with their fallopian tubes, and are more likely to have had pelvic surgery, which can interfere with reproduction.

      While fertility may decline slightly as males age, it is not nearly as dramatic as the decline in women's fertility. Some men can father children decades past the age when women go through menopause.

      Ovulation Disorders

      Some women do not ovulate regularly. This can make getting pregnant more challenging. Women with ovulation disorders are usually aware of them—they may have irregular, unpredictable periods, or may have very long intervals between periods.

      There are three main categories of ovulation disorders: polycystic ovarian syndrome (PCOS), ovarian failure, and hypothalamic amenorrhea.

      Despite the name, polycystic ovarian syndrome has nothing to do with cysts. It has that name because when you examine women who have PCOS with ultrasound, they have what look like tiny cysts on their ovaries. These specks are actually immature eggs. Women with PCOS may have irregular periods or may not menstruate at all. They tend to have high levels of male hormones, and may have facial hair, acne, or other testosterone-related symptoms.

      In ovarian failure, the ovaries simply stop working. This may happen in menopause, but it can also happen earlier. Women with premature ovarian failure have high levels of follicle-stimulating hormone (FSH) in their blood.

      Hypothalamic amenorrhea is a common problem in athletes, ballerinas, or other women who train very hard. "Amenorrhea" means having no periods. "Hypothalamic" means it's related to the hypothalamus, a region of the brain that is sensitive to stress. Very intense physical training or emotional stress can affect menstruation. Eating disorders are another common cause of hypothalamic amenorrhea. It can also be caused by a brain tumor or brain surgery that affects the hypothalamus.

      Egg Quality Disorders

      Some women produce poor-quality eggs. The reasons are often not known. Hormonal or reproductive disorders like endometriosis may contribute, or eggs could be defective because of a woman's genetics or something she has been exposed to in the environment. Doctors usually can't offer an explanation for poor-quality eggs, and the only option for these women may be in vitro fertilization using an egg donor.

      Blocked Fallopian Tubes

      The fallopian tubes are the passage through which an egg moves from the ovaries to the uterus. The fallopian tubes are sensitive to scarring and can be blocked as a result of infection, endometriosis, or scar tissue from previous surgery. This can make the fallopian tube unable to transport an egg into the uterus or sperm from the uterus to the egg.

      Sexually transmitted diseases can cause pelvic inflammatory disease (PID). Scarring from PID can block the fallopian tubes or damage them so they can't pick up an egg from the ovary. Since PID has no symptoms in up to 50 percent of cases, many women will not know that they have had this infection.

      Endometriosis, in which the tissue that lines the uterus grows in other parts of the belly cavity, can also block the fallopian tubes.

      In some cases, a blockage can cause a hydrosalpinx, a fallopian tube filled with fluid. That fluid can leak out of the tube into the uterine cavity, which may make the uterus inhospitable to an embryo. Doctors don't yet know exactly how the fluid affects fertility, but removing the fallopian tube sometimes helps.


      Endometriosis occurs when endometrial tissue (the endometrium is the lining of the uterus) grows outside of the uterus in the belly cavity. Usually it grows on other reproductive structures but is occasionally found in other areas such as the diaphragm or intestines. Endometriosis may cause painful periods, but many women never know they have it.

      When endometrium is on structures other than the uterus, it still cycles like the uterine lining and bleeds a little every month, introducing blood in places where it doesn't belong. This can cause scarring, cause tissues to stick together that shouldn't do so, and cause inflammation as the body tries to heal the bleeding spot. The symptoms of endometriosis usually go away during pregnancy because the tissues do not cycle during pregnancy, but it tends to come back afterward.

      Endometriosis does not always cause infertility; some women have only mild endometriosis and can't get pregnant at all, while others with more severe endometriosis are able to get pregnant. Doctors also don't completely understand how endometriosis affects fertility.

      The causes of endometriosis are unknown, although there appears to be a genetic link. Also, women who have a uterine abnormality may be at higher risk.

      Uterine anomalies

      Uterine anomalies may be problems a woman is born with or that develop over time. For example, there can be congenital problems where the uterus doesn't form properly, so the uterine cavity can't carry a pregnancy to term. This usually leads to miscarriages rather than to an inability to get pregnant in the first place. In some women, the opening to the fallopian tube may not form correctly, or the cervix may not form correctly. These are relatively rare abnormalities.

      Some uterine anomalies develop as you get older. This could include scar tissue, polyps, fibroids, or other growths that affect the endometrium or the cavity of the uterus, or interfere with implantation.

      Fibroids are noncancerous tumors that grow in the uterus. They are extremely common; some 30 to 50 percent of women of reproductive age have fibroids, and fibroids are rarely the culprit in infertility. Women having infertility treatment may not need to have fibroids removed.


      Just as the legs can have varicose veins, testicles can have them as well. A varicose vein in the testicle is called a varicocele. It is the most common cause of male infertility. A varicocele forms when the valves in the vein, which are supposed to keep blood flowing toward the heart, don't function as they should. When the man stands up or strains, the blood goes back down toward the testicles, forming a varicocele.

      A varicocele probably causes infertility by raising the temperature in the scrotum. Normally, the temperature in the scrotum is about degree or a degree and a half lower than that in the rest of the body, which is important for the cells that produce the sperm. The excess blood in the vein raises the temperature of the testicles and leads to lower sperm motility, abnormal-looking sperm, and low sperm count.

      Most men with a varicocele do not know they have it, but a doctor can feel it in a physical exam. A varicocele can be repaired, or sperm can be extracted from the testicles and used in in vitro fertilization.


      Another common cause of infertility in men is performance-enhancing drugs. Some men take steroids, particularly testosterone, to gain more muscle mass. But testosterone has actually been tested as a method of birth control for men. The pituitary uses testosterone levels to monitor the testicles' performance. If the pituitary recognizes high testosterone levels, it will secrete less of the hormones that tell the testicles to make testosterone. The testicles shrink and may stop making sperm entirely. Effects of steroids may linger for decades.

      Testicular problems

      Some patients make enough sperm, but the sperm are not able to get out of the testicle into the ejaculate. Some boys are born with various conditions in which the different tubes fail to connect correctly. The patients have normal testosterone production but no sperm. Men who carry the gene for cystic fibrosis sometimes have an abnormality in the vas deferens, which carries sperm to the urethra. Blockages can also happen accidentally during surgery. Also, men who have had vasectomies produce sperm but have no sperm in their ejaculate.

      Some men's bodies produce low-quality sperm or don't make sperm at all. For example, men with a condition called Sertoli-cell-only syndrome produce no sperm because they have Sertoli cells (which nourish sperm as they grow) but not the cells that actually produce sperm.

      Chemotherapy and radiation therapy

      Chemotherapy and radiation therapy for cancer, which wipe out the rapidly-dividing cells in a tumor, can also kill off the rapidly-dividing cells that give rise to sperm. Young men who are going to have chemotherapy or radiation therapy may wish to bank sperm ahead of time.

      Similarly, chemotherapy and radiation therapy can affect the ovaries. Women are born with all the eggs they will have. Chemotherapy and radiation can destroy eggs, which cannot be replaced. It is possible to freeze eggs, but this technology is not available everywhere. Read more about freezing eggs in the treatment section. If the ovaries are to be removed, it may be possible to freeze ovarian tissue.

      Risk factors

      A woman's age is the single most important risk factor for infertility. Women are most fertile in their teens and 20s. Fertility may begin to decline slightly in the late 20s and declines more rapidly in the late 30s.

      If a woman's mother had menopause before the age of 40, she also may be at risk of losing her fertility early.

      Last reviewed on 03/31/2007

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