Contraception

The development of oral contraceptives has been credited with helping to launch the sexual revolution of the 1960s. Whether oral contraceptives, also known as "the pill," should take credit for broadening sexual activity or not, their development changed the contraceptive world dramatically. In 1988, oral contraceptives were the Variety of contraceptive methods. Photograph by Michael Keller. The Stock Market. Reproduced by permission. most popular reversible contraceptive in the United States, with 30.7% of all women who used birth control using them, second only to sterilization. That rate dropped to 26.9% by 1995. The accidental pregnancy rate among women using oral contraceptives is less than 3%.

The development of oral contraceptives incorporated great advances in basic scientific knowledge. These included the finding in 1919 that transplanted hormones made female animals infertile, and the isolation in 1923 of estrogen, the female sex hormones.

For years, the knowledge that hormones could make animals infertile could not be applied to humans because of the expense of obtaining naturally-occurring estrogen. Until chemist Russell Marker developed a technique for making estrogen from plant steroids in 1936, estrogen had to be obtained from animal ovaries. Scientists needed ovaries taken from 80,000 sows to manufacture a "fraction of a gram" of estrogen.

Once synthetic hormones were available, the creation of oral contraceptives was limited by a lack of interest in the development of new birth control devices among drug companies and other conventional funding sources. Gregory Pincus (1903–1967), who developed the oral contraceptive, obtained only limited funding from a drug company for his research. The bulk of his funding was from Katherine McCormick, a philanthropist, suffragist and Massachusetts Institute of Technology graduate who was committed to broadening birth control options.

The birth control pill, approved for use in the United States in 1960, uses steroids to alter the basic reproductive cycle in women. Pincus knew that steroids could interrupt the cyclic release of a woman's eggs during ovulation. Most pills use a combination of synthetic estrogen and progestin, although some only contain progestin. The steady levels of estrogen and progestin, obtained through daily oral contraceptive doses, prevent the release from the hypothalamus of gonadotrophin, a hormone which triggers ovulation. The pill also changes the cervical mucus so it is thicker and more difficult for sperm to penetrate.

Oral contraceptives can cause weight gain, nausea and headaches. In addition, women who smoke and are over 35 are advised not to take oral contraceptives due to risk of stroke. Oral contraceptives slightly increase the risk of cervical cancer, but they decrease the risk of endometrial and ovarian cancers.

Other contraceptives have drawn from oral contraceptive technology, including several which work for a long period of time and do not require daily doses of hormones. Norplant, approved for use in the United States in 1991, is a hormone-based contraceptive which is surgically implanted in the arm and which lasts approximately five years. It distributes a steady dose of the hormone progestin, which inhibits ovulation and alters cervical mucus to reduce movement of the sperm. The implant is highly effective. Of the 1.3% users in 1995, the accidental pregnancy rate was less than 0.95%. However, the side affects include excess bleeding and discomfort, which sometimes force removal of the device, and difficulty in removing the implants.

Several long-term contraceptives are injectable and also use progestin to inhibit ovulation. The most widely used is Depo-Medroxyprogesterone Acetate, also known as Depo-Provera or DMPA. The method is used in more than 90 countries but not widely in the United States. The drug, which is given every three months, is popular internationally, with as many as 3.5 million users worldwide. Fewer than 0.3% of women taking DMPA get pregnant accidentally. Most women who take DMPA for long periods of time stop having a regular menstrual cycle. The drug also causes temporary infertility after use.