EXPLANATION
Contraceptives have both a theoretical effectiveness, which is a lab-tested value, and an actual effectiveness, which is how well they perform when used by actual people. In terms of contraceptive methods, intrauterine devices have a 99% theoretical effectiveness, and about a 97% actual effectiveness, making it one of the most effective methods of birth control available. Other benefits include its temporary nature and minimal side effects.
Other widely used methods for fertility control include barrier methods. These include diaphragms, sponges, condoms, and the cervical cap. Although the theoretical effectiveness of these methods is high (about 94-98%), their actual effectiveness is probably somewhere in the high 80s due to user error.
The morning-after pill (Plan B) is used after unprotected intercourse, but it has been shown to not be as statistically effective as the oral contraceptive pill taken as directed. It is also not intended for repeated use.
REFERENCES
- Hall JE. Infertility and Contraception. In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J, et al., eds. Harrison's Principles of Internal Medicine. 19th ed. New York: McGraw-Hill; 2015.
- Hoffman BL, Schorge JO, Schaffer JI, et al. Chapter 5. Contraception and Sterilization. Williams Gynecology. 2nd ed. New York: McGraw-Hill; 2012.