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22.10: Infertility

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  • Family Portrait

    This family portrait in Figure \(\PageIndex{1}\) shows that human societies value having children. Indeed, for most people, parenthood is an important life goal. Unfortunately, some people are unable to achieve that goal because of infertility.

    Family portait

    Figure \(\PageIndex{1}\): Family portrait

    What Is Infertility?

    Infertility is the inability of a sexually mature adult to reproduce by natural means. For scientific and medical purposes, infertility is generally defined as the failure to achieve a successful pregnancy after at least one year of regular, unprotected sexual intercourse. Infertility may be primary or secondary. Primary infertility applies to cases in which an individual has never achieved a successful pregnancy. Secondary infertility applies to cases in which an individual has had at least one successful pregnancy, but fails to achieve another after trying for at least a year. Infertility is a common problem. About ten percent (6.1 million) of U.S. women aged 15 to 44 have difficulty getting or staying pregnant.

    Causes of Infertility

    Infertility causes pie chart
    Figure \(\PageIndex{2}\): Infertility affects males as often as females and that the cause of infertility often is unexplained

    Pregnancy is the result of a multi-step process. In order for a normal pregnancy to occur, an egg must be released from one of the ovaries, the egg must go through a Fallopian tube, a sperm must fertilize the egg as it passes through the Fallopian tube, and then the fertilized egg must implant in the uterus. If there is a problem with any of these steps, infertility can result.

    A couple’s infertility may be due to a problem with either partner. As shown in Figure \(\PageIndex{2}\), about 30 percent of infertility cases are due to female infertility, and about 30 percent are due to male infertility. Most of the remaining 40 percent of cases are due to a combination of male and female problems or unknown causes.

    Causes of Male Infertility

    Male infertility occurs when there are no or too few sperms, or when the sperms are not healthy and motile and cannot travel through the female reproductive tract to fertilize an egg. A common cause of inadequate numbers or motility of sperm is varicocele, which is an enlargement of blood vessels in the scrotum. This may raise the temperature of the testes and adversely affect sperm production. In other cases, there is no problem with the sperm, but there is a blockage in the male reproductive tract that prevents the sperm from being ejaculated.

    Factors that increase a man’s risk of infertility include heavy alcohol use, drug abuse, cigarette smoking, exposure to environmental toxins (such as pesticides or lead), certain medications, serious diseases (such as kidney disease), and radiation or chemotherapy for cancer. Another risk factor is advancing age. Male fertility normally peaks in the mid-twenties and gradually declines after about age 40, although it may never actually drop to zero.

    Causes of Female Infertility

    Female infertility generally occurs due to one of two problems: failure to produce viable eggs by the ovaries, or structural problems in the Fallopian tubes or uterus. The most common cause of female infertility is a problem with ovulation. Without ovulation, there are no eggs to be fertilized. Anovulatory cycles (menstrual cycles in which ovulation does not occur) may be associated with no or irregular menstrual periods, but even regular menstrual periods may be anovulatory for a variety of reasons. The most common cause of anovulatory cycles is polycystic ovary syndrome (PCOS), which causes hormone imbalances that can interfere with normal ovulation. Another relatively common cause of anovulation is primary ovarian insufficiency. In this condition, the ovaries stop working normally and producing viable eggs at a relatively early age, generally before the age of 40.

    Structural problems with the Fallopian tubes or uterus are less common causes of infertility. The Fallopian tubes may be blocked as a result of endometriosis. Another possible cause is a pelvic inflammatory disease, which occurs when sexually transmitted infections spread to the Fallopian tubes or other female reproductive organs (Figure \(\PageIndex{3}\)). The infection may lead to scarring and blockage of the Fallopian tubes. If an egg is produced and the Fallopian tubes are functioning — and a woman has a condition such as uterine fibroids — implantation in the uterus may not be possible. Uterine fibroids are non-cancerous clumps of tissue and muscle that form on the walls of the uterus.

    Factors that increase a woman’s risk of infertility include tobacco smoking, excessive use of alcohol, stress, poor diet, strenuous athletic training, and being overweight or underweight. Advanced age is even more problematic for females than males. Female fertility normally peaks in the mid-twenties, and continuously declines after age 30 and until menopause around the age of 52, after which the ovary no longer releases eggs. About one-third of couples in which the woman is over age 35 have fertility problems. In older women, more cycles are likely to be anovulatory, and the eggs may not be as healthy.

    Pelvic Inflammatory Disease swollen Fallopian tubes
    Figure \(\PageIndex{3}\): An infection of the Fallopian tubes may cause scarring and blockage of the tubes, so sperm cannot reach eggs for fertilization.

    Diagnosing Causes of Infertility

    Diagnosing the cause(s) of a couple’s infertility often requires testing both partners for potential problems. The semen is likely to be examined for the number, shape, and motility of sperm. If problems are found with sperm, further studies are likely to be done, such as medical imaging to look for structural problems with the testes or ducts.

    In individuals with ovaries and uterus, the first step is most often determining whether ovulation is occurring. This can be done at home by carefully monitoring body temperature (it rises slightly around the time of ovulation) or using a home ovulation test kit, which is available over the counter at most drugstores. Whether or not ovulation is occurring can also be detected with blood tests or ultrasound imaging of the ovaries. If ovulation is occurring normally, then the next step may be an X-ray of the Fallopian tubes and uterus to see if there are any blockages or other structural problems. Another approach to examining the reproductive tract for potential problems is laparoscopy. In this surgical procedure, a tiny camera is inserted into the abdomen through a small incision. This allows the doctor to directly inspect the reproductive organs.

    Treating Infertility

    Infertility often can be treated successfully. The type of treatment depends on the cause of infertility.

    Treating Male Infertility

    Medical problems that interfere with sperm production may be treated with medications or other interventions that may lead to the resumption of normal sperm production. If, for example, if an infection is interfering with sperm production, antibiotics may resolve the problem. If there is a blockage in the ejaculation of sperm, surgery may be able to remove the blockage. Alternatively, the sperm may be removed from his body and then used for the artificial insemination of their partner. In this procedure, the sperms are injected into the uterus.

    Treating Female Infertility

    It is possible to correct blocked Fallopian tubes or uterine fibroids with surgery. Ovulation problems, on the other hand, are usually treated with hormones that act either on the pituitary gland or on the ovaries. Hormonal treatments that stimulate ovulation often result in more than one egg being ovulated at a time, thus increasing the chances of a person conceiving with twins, triplets, or even higher multiple births. Multiple fetuses are at greater risk of being born too early or having health and developmental problems. The mother is also at greater risk of complications arising during pregnancy. Therefore, the possibility of multiple fetuses should be weighed in making a decision about this type of infertility treatment.

    egg removal from female for assistive reproduction
    Figure \(\PageIndex{4}\): This figure shows one way ART procedures may be used to treat infertility. An egg is removed from the female reproductive tract, injected with sperm from her partner, and allowed to develop into an embryo in the lab. Then, the embryo is placed inside the woman’s uterus for implantation and development during the remainder of gestation.

    Assisted Reproductive Technology

    Some cases of infertility are treated with assisted reproductive technology (ART). This is a collection of medical procedures in which eggs and sperms are removed to be manipulated in ways that increase the chances of fertilization occurring. The eggs and sperm may be injected into one of the Fallopian tubes for fertilization to take place in vivo (in the body). More commonly, however, the eggs and sperm are mixed together outside the body so fertilization takes place in vitro (in a test tube or dish in a lab). The latter approach is illustrated in Figure \(\PageIndex{4}\). With in vitro fertilization, the fertilized eggs may be allowed to develop into embryos before being placed in the woman’s uterus.

    ART has about a 40 percent chance of leading to a live birth in women under the age of 35, but only about a 20 percent chance of success after the age of 35. Some studies have found a higher-than-average risk of birth defects in children produced by ART procedures, but this may be due to the generally higher ages of the parent — not the technologies used. Same-sex couples take advantage of the ART process to expand their family. 

    Other Approaches

    Other approaches for certain causes of infertility and same-sex couples include the use of a surrogate mother, a gestational carrier, or sperm donation.

    • A surrogate mother is a woman who agrees to become pregnant using the man’s sperm and her own egg. The child, who will be the biological offspring of the surrogate and the male partner, is given up at birth for adoption by the couple. Surrogacy might be selected by women with no eggs or unhealthy eggs. A woman who carries a mutant gene for a serious genetic disorder might choose this option to ensure that the defective gene is not passed on to the offspring.
    • A gestational carrier is a woman who agrees to receive a transplanted embryo from a couple and carry it to term. The child, who will be the biological offspring of the couple, is given to the parents at birth. A gestational carrier might be used by women who have normal ovulation but no uterus, or who cannot safely carry a fetus to term because of a serious health problem (such as kidney disease or cancer). This method is commonly used by gay men couples. 
    • Sperm donation is the use of sperm from a fertile man (generally through artificial insemination) for cases in which the male partner in a couple is infertile, or in which a woman seeks to become pregnant without a male partner. A lesbian couple may use donated sperm to enable one of them to become pregnant and have a child. Sperm can be obtained from a sperm bank, which buys and stores sperm for artificial insemination, or a male friend or another individual may donate sperm to a specific woman.

    Social and Ethical Issues Relating to Infertility

    For people who have a strong desire for children of their own, infertility may lead to deep disappointment and depression. Individuals who are infertile may even feel biologically inadequate. Partners in infertile couples may argue and feel resentment toward each other, and married couples may get divorced because of infertility. Infertility treatments — especially ART procedures — are generally time-consuming and expensive. The high cost of the treatments can put them out of the financial reach of many couples.

    Ethical Concerns

    Some people question whether the allocation of medical resources to infertility treatments is justified and whether the resources could be better used in other ways. The status of embryos that are created in vitro and then not used for pregnancy is another source of debate. Some people oppose their destruction on religious grounds, and couples may sometimes argue about what should be done with their extra embryos. Ethical issues are also raised by procedures that increase the chances of multiple births, because of the medical and developmental risks associated with multiple births.

    Infertility in Developing Countries

    Infertility is an under-appreciated problem in the poorer nations of the world, because of assumptions about overpopulation problems and high birth rates in developing countries. In fact, infertility is at least as great a problem in developing as in developed countries. High rates of health problems and inadequate health care in the poorer nations increase the risk of infertility. At the same time, infertility treatments are usually not available — or are far too expensive — for the vast majority of people who may need them. In addition, in many developing countries, the production of children is highly valued. Children may be needed for family income generation and economic security of the elderly. It is not uncommon for infertility to lead to social stigmatization, psychological problems, and abandonment by spouses.

    Feature: Human Biology in the News

    More than 14 million people in the United States have polycystic ovary syndrome (PCOS), an endocrine disorder with a genetic basis that is the most common cause of infertility. Most patients with PCOS grow many small cysts on their ovaries. The cysts are not usually harmful, but they lead to hormone imbalances, such as higher-than-normal levels of testosterone in affected individuals. The hormonal imbalances are the primary cause of infertility associated with PCOS. The disorder also increases the risk of a whole slew of other serious health problems, including endometrial cancer, heart disease, high blood pressure, type 2 diabetes, asthma, obesity, depression, and anxiety.

    Despite the prevalence of PCOS and its serious potential effects, until recently, its cause was poorly understood. There were also no effective early diagnostic or treatment strategies for it. All that appears to be changing now. A review of the research literature on PCOS published in 2016 provides new insights into causes, diagnosis, and treatment for the disorder.

    Among the research cited in the review is promising new work on nonhuman animal models, including monkeys and mice. One line of research suggests that PCOS may be programmed into a fetus during the second trimester of pregnancy. Another line of research indicates that hair taken from an infant can be analyzed for early risk factors for PCOS, even though PCOS symptoms do not show up until puberty. In addition, the research is helping scientists identify a constellation of genes that are suspected to play a role in PCOS.

    The new research on PCOS is important for those who suffer from the disorder and its consequences, including infertility and life-threatening chronic conditions (such as heart disease and diabetes). The hope is that such research will lead to new ways of diagnosing PCOS at an early age, when medical interventions and lifestyle choices may be used to head off the more serious complications. It is likely that the research will also eventually lead to new and more effective treatment options for the millions of people who battle PCOS.


    • Infertility is the inability of a sexually mature adult to reproduce by natural means. It is defined scientifically and medically as the failure to achieve a successful pregnancy after at least one year of regular, unprotected sexual intercourse.
    • About 30 percent of infertility in couples is due to female sex infertility and another 30 percent is due to male sex infertility. In the remaining cases, a couple’s infertility is due to problems in both partners, or to unknown causes.
    • Male infertility occurs when there are no or too few healthy, motile sperm. This may be caused by problems with spermatogenesis, or by blockage of the male reproductive tract that prevents sperm from being ejaculated. Risk factors for male infertility include heavy alcohol use, smoking, certain medications, and advancing age, to name just a few.
    • Female infertility occurs due to failure to produce viable eggs by the ovaries, or structural problems in the Fallopian tubes or uterus. Polycystic ovary syndrome is the most common cause of failure to produce viable eggs. Endometriosis and uterine fibroids are possible causes of structural problems in the Fallopian tubes and uterus. Risk factors for female infertility include smoking, stress, poor diet, and older age, among others.
    • Diagnosing the cause(s) of a couple’s infertility generally requires testing both the man and the woman for potential problems. For men, semen is likely to be examined for adequate numbers of healthy, motile sperm. For women, signs of ovulation are monitored, for example, with an ovulation test kit or ultrasound of the ovaries. For both partners, the reproductive tract may be medically imaged to look for blockages or other abnormalities.
    • Treatments for infertility depend on the cause. For example, if a medical problem is interfering with sperm production, medication may resolve the underlying problem so sperm production is restored. Blockages in either the male or the female reproductive tract can often be treated surgically. If there are problems with ovulation, hormonal treatments may stimulate ovulation.
    • Some cases of infertility are treated with assisted reproductive technology (ART). This is a collection of medical procedures in which eggs and sperm are taken from the couple and manipulated in a lab to increase the chances of fertilization occurring and an embryo forming. Other approaches for certain causes of infertility include the use of a surrogate mother, gestational carrier, or sperm donation.
    • Infertility can negatively impact a couple socially and psychologically, and it may be a major cause of marital friction or even divorce. Infertility treatments may raise ethical issues relating to the costs of the procedures and the status of embryos that are created in vitro,but not used for pregnancy. Infertility is an under-appreciated problem in developing countries, where birth rates are high and children have high economic — as well as social — value. In these countries, poor health care is likely to lead to more problems with infertility and fewer options for treatment.


    1. What is infertility? How is infertility defined scientifically and medically?
    2. What percentage of infertility in couples is due to male infertility? What percentage is due to female infertility?
    3. Identify causes of and risk factors for male infertility.
    4. Identify causes of and risk factors for female infertility.
    5. How are the causes of infertility in couples diagnosed?
    6. How is infertility treated?
    7. Discuss some of the social and ethical issues associated with infertility or its treatment.
    8. Why is infertility an under-appreciated problem in developing countries?
    9. Describe two similarities between the causes of male and female infertility.
    10. True or False: A person who already has a biological child can suffer from infertility.
    11. True or False: ART always involves fertilization outside of the body.
    12. Explain the difference between males and females in terms of how age affects fertility.
    13. If a woman has no viable eggs, which method below is the most likely to help her and her partner have a baby?
      1. gestational carrier
      2. surrogate mother
      3. in vitro fertilization
      4. in vivo fertilization
    14. Do you think that taking medication to stimulate ovulation is likely to improve fertility in cases where infertility is due to endometriosis? Explain your answer.
    15. If a semen sample shows no sperm, what is a possible cause?
      1. blockage in the male reproductive tract
      2. lack of spermatogenesis
      3. PCOS
      4. A and B

    Explore More

    A new study shows that men who smoke marijuana more than once a week have sperm counts around 33 percent lower than men that don't. Learn more here:

    Check out this video to watch an embryo created with in vitro fertilization developing over five days:


    1. Family Portrait by taylormackenzie via CC BY-SA 2.0
    2. Causes of infertility by Häggström, Mikael (2014). "Medical gallery of Mikael Häggström 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.008. ISSN 2002-4436. Public Domain. via Wikimedia Commons
    3. Pelvic Inflammatory Disease by staff (2014). "Medical gallery of Blausen Medical 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436CC BY 3.0 via Wikimedia Commons 
    4. Assisted Reproductive Technology by staff (2014). "Medical gallery of Blausen Medical 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436CC BY 3.0 via Wikimedia Commons 
    5. Text adapted from Human Biology by CK-12 licensed CC BY-NC 3.0