Benefits & Risks in Oral Contraceptives

A. History

Oral contraceptives (OCs), also known as the pill, have been available in the United States since 1960. They have become the most widely used types of reversible contraception in this country. In 1995, some 27% of American woman of childbearing age (15 to 44 years of age) who used contraception used OCs. Over the last 2 decades, the amount of both estrogen and progestin contained in the pills have been reduced considerably compared with the early OCs.

B. Benefits of Oral Contraceptives

• Contraceptive Efficacy
• Non-Contraceptive Benefits

Contraceptive Efficacy

OCs are among the most effective means of contraception (Table 1). When used correctly, combination OCs have a failure rate of only 0.1% in the first year of use. This is 60 times more effective than using a diaphragm and 30 times more effective than relying on a condom. In contrast to sterilization, the effect of OCs is more easily reversed.

Progestin-only OCs are somewhat less effective than combination OCs, with a 0.5% pregnancy rate after 1 year of correct use. Even when patients use OCs incorrectly (eg, by forgetting to take a pill or taking a pill out of sequence), the failure rate for both combination and progestin-only OCs is still just 5%.

Non-contraceptive Benefits

In addition to contraception, OCs provide other noncontraceptive benefits to users. OC use has been associated with a lower incidence of ovarian cancer (Table 2). Women who use OCs have about half the risk of developing ovarian cancer as do women who never used them. Each successive year of OC use reduces the risk of even further ovarian cancer. The incidence of nonmalignant ovarian cysts is also lower in OC users. Progestin in both combination and progestin-only OCs contributes to a lowered incidence of endometrial cancer and benign breast cysts and tumors. The incidence of endometrial cancer is reduced by 50% after at least 1 year of use.

Women who use OCs have more regular and predictable menstrual cycles, with a reduction in the days and amount of menstrual flow, which in turn reduces the risk of iron deficiency anemia. The incidence of premenstrual syndrome (PMS) may also decrease some in women using oral contraceptives.

Use of OCs has also been shown to lower the incidence of ectopic pregnancy and pelvic inflammatory disease (PID). OC use may also increase bone mineral density, have a modest positive effect on cholesterol levels, raising HDL-cholesterol (the "good" cholesterol) and lowering LDL-cholesterol (the "bad" cholesterol). This is a result of the estrogen component, as some progestins alone have a modest negative effective on cholesterol levels.

C. Risks

• Minor Adverse Effects
• Major Adverse Effects
  

Today's OCs contain one fourth or less of the amount of estrogen and one tenth or less of the amount of progestin as the original OCs introduced in the 1960s. As the amount of estrogen and progestin in OCs has been decreased, the risk of certain adverse effects has also fallen dramatically. Low-dose products are defined as those containing less than 50 mcg of estrogen. The lowest estrogen dose currently available in an OC is 20 mcg.

Minor Adverse Effects

Common minor adverse effects linked to the use of OCs include nausea and breast tenderness (both of which often decrease after several months of use), fluid retention, and depression. Some women also may experience increases in blood pressure, so it should be measured annually.

Progestin in OCs have been linked to weight gain, nervousness, and absence of, or abnormal, menstruation. Both estrogens and progestins appear to contribute to breakthrough bleeding.

Major Adverse Effects

The use of OCs has been linked historically to the incidence of cardiovascular disease--including clogged arteries (atherosclerosis), blood clots (thromboembolism), and heart attacks (myocardial infarction) as well as breast cancer, gallbladder disease, cervical cancer, and benign liver tumors. However, as pills with lower estrogen and progestin content have replaced earlier high-dose formulations, the risks of some of these conditions may not be as great as with older OCs. For example:

• As currently formulated, OCs actually do not promote the development of atherosclerosis. As noted earlier, the positive impact of estrogen on cholesterol levels appears to counter any potential negative impact of progestin.
• The most recent and thorough data suggest that OC use is not linked to breast cancer.
• Currently available OCs do not increase the risk for gallbladder disease.

Some health risks may still exist for users of OCs. These include the following:

• High doses of estrogen may contribute to formation of blood clots that can result in heart attacks and strokes. For the vast majority of woman taking OCs, the amounts of estrogen in today's OCs pose no risk of heart attack or stroke. However, the risk apparently increases dramatically in women who smoke. Other factors that increase the risk are:
• >35 years of age
• hypertension
• diabetes
• high cholesterol
• It is recommended that women older than 35 years of age who smoke do not use OCs.
• OC users may be at increased risk of developing cervical cancer. These women should receive a yearly examination of cervical tissue, especially if they have been using OCs for at least 5 years.
• Women who have used OCs for longer than 4 years are at increased risk of developing benign liver tumors, although this condition is rare. The tumors disappear if use of the OC is discontinued.