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Surgery => Gynecology => Infertility
Infertility
INTRODUCTION
Infertility, inability to conceive or carry a child to term. About 6.1 million women in the United States have difficulty conceiving and carrying a child to term, and about 2.1 million married couples in the United States are infertile. About a third of infertility cases can be traced to causes in the male, about a third to causes in the female, and the remaining cases to unidentifiable problems or conditions in each partner that interact to cause infertility.
CAUSES
During sexual intercourse, sperm are ejaculated (ejected during orgasm) deep inside the vagina near the cervix, the small organ connecting the vagina and the uterus. The sperm travel through the cervical mucus (thick fluid that helps to protect the cervix and uterus from infection), into the uterus, and up the fallopian tubes (channels connecting the ovaries to the uterus), where fertilization normally occurs. If a sperm is able to penetrate, or fertilize, an egg, and if other conditions are favorable, the fertilized egg will travel from the fallopian tubes to the uterus, where it will implant itself in the uterine lining and fetal development will begin (see Human Sexuality). A problem or obstruction at any point in the process, however, prevents pregnancy from taking place.
Historically, men were assumed to be fertile if they were capable of sexual intercourse. As a partial consequence of this attitude, past research on fertility has emphasized problems in women. Low sperm count, however, is a common cause of infertility among couples, and the most frequent cause of male infertility. Although only one sperm is ultimately required for fertilization, men whose semen (fluid composed of sperm and other secretions and produced during ejaculation) contains less than 20 million sperm per milliliter frequently have infertility problems. The most common problem affecting male sperm levels is a varicocele, a tangle of swollen veins surrounding the testis (the reproductive organ that produces sperm). Surgical correction of the varicocele restores normal fertility in about two-thirds of cases.
Other sperm problems affect male fertility. The sperm may not be viable-that is, structurally healthy and capable of fertilization; it may be viable but unable to move correctly; it may contain the wrong number of chromosomes, the packets of genetic information; or it may have been stored too long after its formation. The vas deferens (tubes that carry sperm from the testes to the penis) may be blocked because of a past infection or injury. The man may not be able to ejaculate or his ejaculation may propel the sperm backward into his bladder rather than out through the penis. Other causes of male infertility include insufficient hormone levels, which can be supplemented with oral hormone treatments; prostate disease; untreated diabetes; or other medical conditions.
Once inside the female's cervix, the sperm may encounter mechanical or chemical obstacles. A muscle spasm may eject the sperm, the cervical mucus may be too thick for the sperm to penetrate, or it may be chemically hostile to the sperm. The fallopian tube may be blocked by scar tissue, preventing the sperm from reaching the egg. If the sperm does manage to reach the egg, it may not be able to penetrate the egg's defenses to fertilize it. A fertilized egg may become stuck in the fallopian tube or it may not be able to implant successfully in the uterus.
In women, one of the most frequent causes of infertility is abnormal ovulation, or irregular release of an egg (ovum) from the ovary. Normally one egg will be released each month under the direction of several hormones about midway through the menstrual cycle (see Menstruation). If any of these hormones are not functioning, ovulation will occur irregularly, or perhaps not at all. This condition accounts for about 25 percent of cases of female infertility. Another frequent cause is blocked fallopian tubes, accounting for about 35 percent of infertility cases.
According to the Centers for Disease Control and Prevention (CDC), the incidence of infertility has not changed significantly in recent years. The perception that infertility is on the rise is probably due in part to a broader awareness of the issue-increasing numbers of couples are seeking medical assistance for infertility. In addition, there is a growing tendency to delay childbearing, often until women are in their 30s. A woman reaches her peak fertility at the age of 18 or 19, with little change until the mid-20s. Fertility then begins a slow decline to age 35 (about 33 percent of couples in their late 30s are infertile), a sharper decline to age 49, and a very rapid drop as a woman nears menopause. A man's fertility decline is not as rapid and has no clear-cut end point, but a man of 50 is likely to be less fertile than he was at age 25 or 30.
Physicians, usually gynecologists for women and urologists for men, also cite other factors that make infertility seem more common than it actually is. These include a recent surge in the incidence of sexually transmitted diseases, which can severely damage both male and female reproductive systems if left untreated; and the use of birth control pills and intrauterine devices for contraception, which can result in temporary or permanent infertility after their use has been terminated.
DIAGNOSIS
Even among fertile couples the chance of conception in any given month is only about 20 percent, or one chance in five. To avoid unnecessary testing and treatment, most doctors will not make the diagnosis of infertility until one year of unprotected intercourse has failed to result in pregnancy. Cases that involve older couples or fertility evidence from previous relationships may be easier to diagnose sooner and to treat more aggressively. Once the diagnosis of infertility is made, examinations, tests, and medical histories are all used to find its cause.
Male fertility will often be tested first. The semen is tested to determine the quantity and health of sperm. Women undergo a physical and pelvic examination, laboratory tests, and one or more imaging procedures to locate the problem that may be causing infertility. Testing in women may include exploratory surgery, which is now made easier by the use of the laparoscope, a small fiber-optic tool that is inserted through a small incision and enables a physician to inspect the reproductive system. Advanced ultrasound imaging may also reveal structural or functional problems. One such condition is endometriosis, in which cells from the endometrium (lining of the uterus) spread in patches and cysts throughout the female reproductive system. Tests may also reveal irregular ovulation or dysfunctional eggs.
TREATMENT
Once the cause of infertility is determined, doctors devise a strategy for the couple to increase their fertility. The optimum treatment is one that enables existing natural reproductive processes to take place. Sometimes only small adjustments in the frequency and timing of sexual intercourse are required to bring about fertilization. Patients are instructed in how to identify the woman's most fertile times in order to plan intercourse accordingly. Practices that temporarily result in lowered sperm counts or damaged sperm can be curtailed, such as the use of certain medications, alcohol, marijuana, and hot tubs or saunas. If the problem is insufficient sperm, a semen sample can be concentrated-that is, the number of sperm per milliliter can be boosted using laboratory techniques to increase potency.
Ovulation problems can be treated with hormones and fertility drugs to produce multiple mature eggs. Fertility drugs, such as clomiphene and human menopausal gonadotropin (HMG), induce ovulation in women whose sex hormones-estrogen, follicle stimulating hormone (FSH), and luteinizing hormone (LH)-do not function properly. HMG may also be given to men to stimulate sperm production. Another fertility drug, a pure, injectable form of FSH, is also given to women to stimulate ovulation.
In addition to conventional methods of fertility treatment, there are also several newer techniques, collectively known as assisted reproductive technology (ART). The best known of these is in vitro fertilization (IVF), which involves the mixing of sperm and egg in the laboratory to trigger fertilization outside the human body. In IVF, hormone treatments are given to the female in order to produce multiple eggs. These eggs are removed from the female during an outpatient procedure, then taken to a laboratory and mixed with specially treated semen in a petri dish. The egg and semen mixture is incubated for several days to fertilize. After fertilization takes place, the zygote (fertilized egg) is usually allowed to develop for several more days outside the body and is then introduced into the woman's uterus. After placement in the uterus, the zygote follows the course of normal pregnancy.
Other ARTs are variations on the technology of in vitro fertilization. The choice of one technology over another depends on the specific needs of the couple. Gamete intrafallopian transfer (GIFT) involves taking the ova and sperm and introducing them directly to the fallopian tube before fertilization has occurred. Zygote intrafallopian transfer (ZIFT) is similar, except that fertilization has already taken place in the lab and an actual embryo is placed in the fallopian tube. One recent development in ART is intracytoplasmic sperm injection (ICSI). In this procedure a single viable sperm is extracted from a sperm sample and injected into an egg; this allows men with extremely low sperm counts to become fathers. Further advances in ART are expected from the quickly evolving fields of genetics and biotechnology.
ETHICAL ISSUES
The rapid development of new fertilization technology has raised many ethical and legal issues. Philosophers, theologians, and medical ethicists question the right of humans to tamper with natural processes.
Fertility practitioners and their patients have more immediate concerns, such as deciding the fate of unused eggs, sperm, and zygotes. If they are frozen and stored, decisions must be made about how long they will be kept and at whose expense. Further issues involve custody of the eggs if the parents divorce or die.
Some observers fear that the availability of fertilization technologies will give humans the ability to manipulate their genetic heredity. Opponents of reproductive technologies argue that the creation of multiple zygotes and the availability of increased personal genetic information allows for too much intervention in reproductive matters. Certain experimental techniques enable doctors to identify and select sperm, eggs, or embryos before they are implanted. These techniques are now used primarily by couples at risk of having children with a severe genetic disease, but some fear parents will someday be able to select certain idealized standards, such as absence of minor defects or preferred gender.
Some of the ethical questions surrounding abortion also arise in the field of fertility technology. Fertility treatment may result in multiple pregnancies, which can endanger the health of the mother and the babies. When multiple pregnancies occur, it is possible to selectively abort one or more of the embryos in order to improve the survival chances of the others and to reduce the burden on parents of raising quintuplets or sextuplets.
When millions of existing children around the world are orphans and poverty stricken, however, many people question spending thousands of scarce medical-care dollars to enable affluent couples to have babies of their own biological parentage. Health care policymakers debate whether infertility treatment is a basic right that should be paid for by medical insurance, or an elective luxury, similar to cosmetic surgery, available only to those who can pay the price. Some experts have raised concerns that couples who must pay for infertility treatment on their own may pursue more aggressive treatments in order to have a better chance of success. These aggressive treatments may increase the probability of multiple births. However, increasing patient awareness of these issues has generated pressure on insurance companies to increase coverage for diagnosis and treatment of fertility problems.
Because infertility and its treatment raises many ethical issues, and because the treatment itself may involve considerable time, expense, and loss of privacy, many couples find the procedure stressful. Physicians experienced in the field recommend both private counseling and infertility support groups to assist couples through the process.
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