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JAMA Patient Page
January 15, 2014

Oral Contraceptives

JAMA. 2014;311(3):321. doi:10.1001/jama.2013.283505

Oral contraceptives, also called birth control pills, are a safe and reliable option for preventing unwanted pregnancy.

How Do Oral Contraceptives Work?

Most oral contraceptives contain a combination of 2 types of hormones: an estrogen and a progestin. Both of these hormones are naturally found in women’s bodies. There are many different types of estrogens and progestins, and different types of pills contain different combinations, but they all work similarly. Some pills contain only progestin, sometimes called the “mini-pill.”

Who Can Take Oral Contraceptives?

The most important requirement for women taking oral contraceptives is that they must remember to take them every day at approximately the same time of day. Oral contraceptives are not a good form of birth control when doses are missed frequently. Combination oral contraceptives should not be given to women older than 35 years who also smoke, because there is an increased risk of blood clots in these women, or to women who have high blood pressure, heart disease, migraines with auras, liver problems, very high cholesterol, a history of blood clots, a history of stroke, or breast cancer.

How Are Oral Contraceptives Taken?

Oral contraceptives are usually prescribed for 4 weeks at a time, with each 4-week packet containing 4 to 7 days of hormone-free pills. Women get their period during these hormone-free days. Some preparations have “extended” or “continuous” hormone dosing with fewer or no hormone-free days so that women get their periods less than once a month. Oral contraceptives can be started any day of the week and any day of the menstrual cycle. All women who start taking oral contraceptives should first have a pregnancy test to make sure they are not already pregnant. Women should also use “backup” birth control, such as condoms, for 7 days after starting.


If birth control pills are taken perfectly (100% of the time), the chance of pregnancy is 0.1%. However, in the real world, accounting for missed days of use, the chance of pregnancy is about 8% per year.

Side Effects

Side effects of oral contraceptives vary depending on the pills’ hormone levels and types. Some include vaginal spotting and abnormal bleeding (this usually decreases after the first 3 months of use), breast tenderness, bloating, and nausea. Studies have shown that birth control pills do not cause major weight gain.

Oral contraceptives may also have some beneficial effects other than birth control. They can help with irregular or heavy periods, painful periods or premenstrual syndromes, polycystic ovarian syndrome, acne, uterine fibroids, and endometriosis.

Other Considerations

It is important to know that oral contraceptives do not protect against sexually transmitted diseases. Also, some medications (such as some antibiotics, seizure medications, and antidepressants) can change how effective birth control pills are when taken together. Taking oral contraceptives can also change the effectiveness of these other medications, so it is important to tell your doctor about all other medications you are taking. There are many other forms of birth control available. Talk to your doctor if you have questions about oral contraceptives or other forms of birth control.

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Article Information

Source: Speroff L, Darney PD. A Clinical Guide for Contraception. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2011.

Topic: Women’s Health