Contraception: Methods, Efficacy, and Selection
Contraception is the prevention of pregnancy through the use of medications, medical devices, or behaviors. Many different contraceptive options (both hormonal and nonhormonal) exist, allowing individuals to choose a method suited to their medical needs and pregnancy prevention priorities; some methods offer additional noncontraceptive benefits. Although often neglected, easy access to contraception, including emergency contraception, is an important part of medical care for all individuals who require it.
Mechanism of Action
Hormonal and nonhormonal contraception differ in their approach to preventing pregnancy:
- Hormonal contraception: Hormonal contraceptives contain estrogen and/or progestins to prevent ovulation, fertilization, and/or implantation of an embryo. It uses progestin with or without estrogen to prevent conception through one or a combination of the following: prevention of ovulation, thickening of cervical mucus, or creation of an inhospitable intrauterine environment. Examples include the hormonal IUD, combined hormonal contraception, and progestin-only pill, implant, or injection.
- Nonhormonal contraception: Prevents conception without altering natural hormones. Nonhormonal contraceptives include sterilization, the copper IUD, barrier methods of contraception, and behavioral methods of contraception. The mechanism of action depends on the method: Copper IUD involves creation of an inhospitable intrauterine environment; barrier methods provide prevention of sperm reaching the uterus; behavioral methods involve avoidance of sex during the fertile window; and sterilization involves blockage of the passage of gametes.
Overview of Contraceptive Methods
The duration of contraception provided ranges from the length of intercourse (e.g., condoms) to years (long-acting reversible contraception such as IUDs and the progestin implant). All methods of contraception are reversible except sterilization.
| Options | Duration and Efficacy | Additional Information |
|---|---|---|
| Sterilization | Irreversible; Highly effective | Includes Vasectomy (male) and Tubal ligation (female). Nonhormonal and invasive. |
| Long-acting reversible contraceptives (LARC) | Long-lasting (3–12 years); Highly effective | Includes IUD (copper or hormonal) and Progestin implant. The progestin implant is the most effective form of contraception. IUDs can be used as emergency contraception. |
| Progestin-only contraceptive injection | Intermediate-acting (∼ 3 months); Highly effective if used perfectly | Depot medroxyprogesterone acetate (DMPA) injection. Can be self-administered. |
| Short-acting hormonal contraception | Short-acting (daily, weekly, or monthly); Highly effective with perfect use | Includes combined hormonal contraceptives (pill, patch, vaginal ring) and progestin-only pills (POPs). |
| Barrier contraceptives | Only needed at the time of intercourse; High failure rate | Includes External/Internal condoms, Dia phragm, Cervical cap, and Contraceptive sponge. Condoms additionally protect against STIs. |
| Behavioral contraception methods | Short-acting; High failure rate | Includes Fertility awareness-based methods, Coitus interruptus, and Lactational amenorrhea. Free methods. |
Contraceptive Efficacy
The efficacy of contraceptive methods is reported as the contraceptive failure rate, i.e., the percentage of individuals who become pregnant within 12 months of initiating a contraceptive method. It is categorized as follows:
- Failure rate with typical use: includes all individuals using that method regardless of whether it is used correctly and/or consistently.
- Failure rate with perfect use (Pearl index): includes only individuals who use the method correctly and consistently; mainly used in clinical studies.
Without use, 85% of female individuals currently using a contraceptive method would become pregnant within 1 year if contraception were stopped.
Selecting a Method
The choice of contraception involves shared decision-making that balances the individual patient's preferences with the risks of contraceptive use. Choice of method is tailored to patient preference and comorbid medical conditions. To assess the individual, one must consider:
- Future reproductive goals
- Previous experience with contraception
- Past medical history to determine USMEC for contraceptive use
The US Medical Eligibility Criteria (USMEC) for contraceptive use are used to provide risk-based guidance for individuals with coexisting medical conditions. Some contraception is available without a prescription; most require a prescription or a health care professional to fit them.