- Definition. The voluntary prevention of pregnancy (“birth control”).
- Contraceptive options (Figure 12.1) depend primarily on the motivation of the user, but none is 100% effective, immediately available, and low cost. Of the methods, only male and female condoms reduce the risk of sexually transmitted infections.
Oral contraceptives (OCs)
The most popular method of reversible contraception in the USA and the UK.
- Composition. Most are combinations that contain both a synthetic estrogen and a progestin. The progestin-only pill (“minipill”) is less popular since it is associated with a higher incidence of irregular bleeding.
- Administration. For simplicity, the first pill is often taken on the first day of the period, or on the first Sunday after the first day of the period. Thereafter, one tablet is taken every day for a total of 21 days, followed by 7 days of a placebo pill. An anovulatory (withdrawal) bleed will then occur. Most OC preparations contain 28 tablets to allow a woman to take a tablet every day, which reduces mistakes and missed pills. Alternative contraception (typically condoms) is generally advisable when starting OCs.
- Formulations. Recently, some OCs have been designed to induce menses quarterly instead of monthly (Seasonale). Other combined hormone alternatives include a weekly transdermal patch (OrthoEvra), a vaginal ring (NuvaRing) changed every 3 weeks, or a monthly injection (Lunelle; not available in the USA).
- Mechanism of action. All types prevent ovulation through central inhibition of the mid-cycle luteinizing hormone (LH) surge, act peripherally to decrease oviductal function, and thicken cervical mucus.
- Health benefits. OCs reduce menstrual cramps and decrease uterine bleeding. They protect against benign breast disease, prevent formation of ovarian cysts, and reduce the incidence and severity of pelvic inflammatory disease (PID). In addition, OCs reduce the risk of endometrial and ovarian cancer, and possibly endometriosis.
- Side effects. Irregular breakthrough bleeding (especially if doses are missed), nausea, headache, elevated blood pressure, weight gain, breast pain.
- Absolute contraindications. Thromboembolic disease, chronic liver disease, undiagnosed uterine bleeding, pregnancy, and estrogen-dependent neoplasia.
- Relative contraindications.
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