Please note: This archive was last updated in 2005.

RHO archives : Topics : Contraceptive Methods

Oral Contraceptives

Combined oral contraceptives

Modern combined oral contraceptives are made from very low doses of synthetic estrogen and progestin. These combined oral contraceptives (COCs)—often called combined pills, the Pill, and birth control pills—are very effective in preventing pregnancy when taken consistently and correctly (at the same time every day). Their use does not interfere with intercourse. COCs are safe for most women; only some cardiovascular conditions, severe chronic conditions, and heavy smoking in women age 35 and over preclude use of the method. Most conditions that restricted use of high-dose COCs do not apply to low-dose formulations. Some characteristics of COCs are highlighted in the table below. If you are trying to access information about the availability or composition of hormonal contraceptives, check the IPPF worldwide, searchable, online database of hormonal contraceptives at http://contraceptive.ippf.org/(zti22a45haiudn45tj3y5bap)/Default.aspx.

Effectiveness

0.1% to 8% failure rate during the first year of typical use; 0.01% failure rate with perfect use in the first year.

Age limitations

No restrictions on use from menarche to age 40.

Parity limitations

No restrictions on use.

Mode of action

Primarily by inhibiting ovulation; secondary mechanisms include thickening of the cervical mucus, changing endometrium, and reducing sperm transport.

Effect on STI risk

Not protective.

Drug interaction

Certain antiseizure medications (barbiturates, carbamazepine, phenytoin, primidone) and antibiotics (Rifampin and Griseofulvin) may reduce the contraceptive effect of COCs.

Duration of use

Most women can use COCs safely throughout their reproductive years; there is no need for periodic discontinuation.

Return to fertility

Immediately or after slight delay (average 2-3 months).

Combined oral contraceptives (COCs) are among the most intensely investigated family planning products in history. A growing body of research confirms that, in addition to being safe for most women, COCs provide significant noncontraceptive health benefits (Blackburn 2000; IPPF 1998). By reducing menstrual bleeding, COCs help prevent iron deficiency anemia. Recent studies have confirmed that long-term COC use protects against ovarian cancer and endometrial cancer. Results suggest that protection is long-lasting, and may persist for 15 years or more after stopping COC use. Although many previous studies in developed countries indicated a greater risk of liver cancer in women who used combined OCs for a long period of time, new data from several studies suggest the effect of OCs on liver cancer is negligible (MILTS 1997; Blackburn 2000).

Breast and cervical cancer

Although OCs have been proven safe for most women, some health issues remain unresolved—primarily the relationship between OC use and breast or cervical cancer. OC use may hasten the diagnosis of existing breast tumors, perhaps because tumors are more readily detected or tumor growth is accelerated. OC use does not increase lifetime risk of developing breast cancer (Blackburn 2000). For most women, especially those in developing countries, the benefits of effective pregnancy prevention outweigh the very slight increased risk of breast cancer associated with COC use (FHI 1996; IPPF 1998; PATH/Outlook 1997). A recent commentary on this topic concludes that after more than 50 studies, most experts believe that pills have little, if any, effect on the risk of developing breast cancer (Hatcher 2002). Most studies in the past decade have found that long-term OC use is associated with a slight increase in the risk of cervical cancer. However, many researchers believe that this observed association may be part of a larger behavior pattern that increases risk of cervical cancer rather than a causal relationship (PATH/Outlook 1997; IPPF 1998; Blackburn 2000).

Another concern has been the risk of certain diseases of the cardiovascular system. Although COC use does carry the risk of cardiovascular disease, the risk is very small, except in older women (over age 35) who smoke or women with high blood pressure. Research is ongoing to clarify whether the risk of cardiovascular disease varies with lower-dose formulations, long-term use, and use by younger or older women. The new eligibility criteria provide strong guidance on how to screen women at risk of cardiovascular disease so that COCs are provided properly (WHO 1996).

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Progestin-only oral contraceptive pills

Progestin-only oral contraceptive pills, often called progestin-only pills (POPs) and minipills, are estrogen-free oral contraceptives made from very low doses of synthetic progestin. POPs are appropriate for older women, especially smokers who want to use an oral hormonal contraceptive method, women for whom estrogen-containing formulations are not recommended because of side effects, and postpartum or breastfeeding women. POPs are effective in preventing pregnancy when taken consistently and daily, at the same time. Their effectiveness is slightly less than that of COCs, especially in younger women, but effectiveness is high in women over 35 years of age and when use compliance is good. POPs are safe for most women; only a few conditions—pregnancy, unexplained vaginal bleeding, and breast cancer—preclude use of the method. POPs protect against endometrial cancer, decrease pelvic pain during menstruation, and may be protective against pelvic inflammatory disease (Blackburn 2000; IPPF 1998; Blumenthal and McIntosh 1996). Some characteristics of POPs are highlighted below.

Effectiveness

0.5% to 10% failure rate during first year of typical use; 0.5% failure rate with perfect use in the first year.

Age limitations

No restrictions on use for women age 16 and over.

Parity limitations

No restrictions on use.

Mode of action

Primarily by thickening cervical mucus, thereby preventing sperm penetration, and also by inhibiting ovulation.

Effect on STI risk

Not protective.

Drug interaction

Certain antiseizure medications (barbiturates, carbamazepine, phenytoin, primadone) and antibiotics (Rifampin and Griseofulvin) may reduce the contraceptive effect of POPs.

Duration of use

Most women can use POPs safely throughout their reproductive years; there is no need for periodic discontinuation.

Return to fertility

Immediately or after slight delay.

Also see Hormonal Contraception, IUDs, and HIV Risk.

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