When the pill was introduced, it satisfied women's need for convenient, safe, and reliable contraception. There were some problems, however. Some pill users experienced such side effects as headaches, nausea, cramps, irregular menstrual bleeding, breast tenderness, or weight gain. These side effects usually are temporary and are not signs of more serious problems. They can be troubling, however, and have led many women to stop using the pill. Also, research in the 1960s and 1970s suggested that estrogen, in the doses used in early OCs, increased the risk of blood clots, stroke, and heart attack (396, 399, 496). Press reports about these findings created repeated "pill scares" and gave OCs an unwarranted aura of danger (150).

Meanwhile, studies found striking evidence of important noncontraceptive benefits of OC use. Most notably, epidemiological studies in the 1980s demonstrated that OCs provide strong protection against endometrial and epithelial ovarian cancer (see Protection from Some Cancers).

The public remains largely unaware of such benefits. In the US, for example, 65% of women surveyed in 1993 could not name one noncontraceptive benefit of the pill. At the same time, over half of respondents believed that OCs pose serious health risks. Moreover, almost two-thirds thought that pill use was at least as dangerous as childbirth (172, 352), which is not the case for most women (182, 295, 306, 413, 454).

Since their introduction, OCs have offered safe contraception for the great majority of women. Still, to reduce common side effects and to minimize the risk of any serious complications, pharmaceutical companies and health care providers have used three approaches:

• To lower the doses of both estrogen and progestin without compromising effectiveness;
• To develop different new progestins;
• To screen women more specifically and to inform them about side effects that they may experience with OCs.

Lauren Goodsmith

A Moroccan health worker hands packets of pills to a client. In Morrocco pill use has risen substantially, from 14% of married women in 1980 to 32% in 1995. With more than 100 million users worldwide, oral contraceptives remain one of the most popular family planning methods.

The reduction of estrogen doses followed early research that related the likelihood of thromboembolic disorders to the size of the estrogen dose (214). US clinical trials found that estrogen doses as low as 20 µg, combined with a progestin, usually limit pregnancy rates to less than 1 per 100 women per year (27, 28, 39, 141, 209, 248, 400, 404, 499, 543). Also, side effects such as nausea, vomiting, cramps, breast discomfort, and headache occurred less often with less estrogen. Initial menstrual bleeding irregularities are more frequent, however (16, 119, 262, 369).

The progestin doses in OCs vary widely because progestins differ greatly in potency by weight (121). Currently, doses of progestins in the norethindrone family—norethindrone, norethindrone acetate, ethynodiol diacetate, and lynestrenol—range from 0.4 to 2 mg. Pills containing the more potent progestins levonorgestrel, desogestrel, and gestodene use doses of 0.05 to 0.15 mg. The different progestins have somewhat different physiological effects and interact differently with estrogens, possibly modifying the effects of both hormones (48, 467).

Research suggests that lower doses do lower risks for some conditions. For example, as lower-dose pills have come into wider use, findings from epidemi-ologic studies suggest that risks of OC-related venous thrombosis, heart attack, and stroke have declined. Significantly increased risk of heart attack and stroke is limited to women over age 35 who smoke or women who have high blood pressure (see Circulatory System Diseases).