Fertility drugs are prescription medications that stimulate the ovaries to produce eggs. They are also known as ovulation induction medications. Typically in the course of a female monthly cycle, one egg is produced in response to hormonal signals from the brain. This ovulatory function can be disturbed in a variety of medical conditions or with the increasing age of a woman. When ovulation does not proceed normally, female infertility can result and fertility drugs are often used to restore ovulation.
There are two major types of fertility drugs. The first is a drug called clomiphene citrate, which comes in pill form. It was first synthesized in 1956, and approved for clinical use in 1967. The second type is derived from the urine of menopausal women, and is therefore called human menopausal gonadotropins (hMG). It was first clinically used in 1969, and is only available in an injectable form. Although both types of drugs can cause multiple eggs to be produced at one time, this is more common with the hMG drugs, so they are thought of as more potent ovulation inducers and are prescribed only by specialists in infertility treatment.
Clomiphene is generally used to induce ovulation when conception will occur through heterosexual intercourse, or when sperm will be inseminated into a woman's vagina or uterus. The cumulative six-month conception rate with clomiphene approaches 60–75 percent. HMGs can also be used for conception through intercourse or insemination, and cumulative six-cycle conception rates approach 90 percent. HMGs are more commonly used in in vitro fertilization (IVF), where it is important for a woman to produce as many eggs as possible.
Multiple gestation–twin, triplet, or higher order pregnancies–are an important consequence of treatment with fertility drugs. The multiple pregnancy rate with clomiphene is approximately 10 percent, nearly all twins. Multifetal gestation rates are approximately 20–25 percent with hMG use and intercourse or insemination. With IVF, twin rates approach 35 percent, and triplet or higher order pregnancies occur in 6–7 percent of cases. Overall this represents a twentyfold increase in twins and a fifty to one-hundredfold increase in higher order multiples compared to rates of multiples in natural conceptions.
Ovarian hyperstimulation syndrome (OHSS) is another potential complication of fertility drugs. In OHSS women experience massive ovarian enlargement, large shifts in fluid and chemical balance in the body, and occasionally blood clots in major veins. Severe OHSS occurs in 1–2 percent of women undergoing fertility drug treatment, and can require hospitalization. In rare cases OHSS can lead to death.
Questions have been raised about the possible association of fertility drugs with later development of ovarian cancer. Several retrospective studies concerning this association offer contradictory conclusions. As a result, the American Society for Reproductive Medicine–the major organization of infertility physicians in the United States–recommends that physicians caution patients that these medications may increase their lifetime risk of developing ovarian cancer.
Data from the National Survey of Family Growth (NSFG), the only source for up-to-date nationally representative infertility data, indicates that approximately 1.8 million U.S. women used ovulation-inducing medications in 1995, the last year for which data is available. Several social trends have influenced the use of fertility medications. First, there has been a recent increase in infertility rates, according to NSFG data. In 1995, 10 percent of women reported some form of fertility impairment, compared to 8 percent in 1988. This rate increase occurred across almost all age, marital status, income, and racial subgroups. This is the first year that the NSFG showed an increase in infertility rates since the survey began in 1973. It is unknown if this increase represents a "real" increase in infertility status or a change in recognition and reporting of fertility problems.
Second, there was a dramatic increase in absolute numbers of women with impaired fertility, out of proportion to the infertility rate change. The number of women with impaired fertility rose from 4.6 million to 6.2 million between 1988 and 1995. It is thought that the dramatic increase in numbers is due to delayed marriage and delayed childbearing trends among the baby boom cohort, who reached their less fertile reproductive years in the 1990s. Third, because older women attempting reproduction have fewer years in which to accomplish childbearing, baby boomers have pursued infertility therapies in great numbers. In 1995, 2.7 million women in the United States sought infertility services, compared to 1.8 million in 1982. Women who sought infertility services tended to be older, married, wealthier, and white.
See also: Conception and Birth; Multiple Births.
Chandra, Anjani, and Elizabeth Stephen. 1998. "Impaired Fecundity in the United States: 1982–1995." Family Planning Perspectives 30, no. 1: 34–42.
Speroff, Leon, Robert Glass, and Nathan Kase. 1999. Clinical Gynecologic Endocrinology and Infertility, 6th ed. Philadelphia: Lipincott Williams and Wilkins.
American Society for Reproductive Medicine. 2002. Available from <www.asrm.org>.
National Survey of Family Growth. 2002. Available from <www.cdc.gov/nchs/nsfg.htm>.
Lisa H. Harris