What Are Birth Control Pills?
Louise Chang, MD
Dr. Chang completed her undergraduate degree at Stanford University and attended medical school at New York Medical College. She completed her internal medicine residency at Saint Vincent's Hospital in New York City, where she also served as a chief resident from 2001-2002. Dr. Chang is board-certified in internal medicine.
- What are birth control pills and how do they work?
- What are the different types of birth control pills?
- Are there differences among birth control pills?
- What are the side effects/health risks of birth control pills?
- What are the drug interactions of birth control pills?
What are birth control pills and how do they work?
Birth control pills are also known as oral contraceptives (OCs) or, simply, “the pill.” They offer protection against pregnancy by blocking the union of sperm and egg, thereby preventing conception.
Oral contraceptives or birth control pills contain synthetic female hormones. They work largely by preventing the release of an egg from an ovary, or ovulation. If no egg is released, there can be no pregnancy.
Stopping ovulation is not the only way birth control pills can work. The progestin or synthetic progesterone in birth control pills also changes the physical and chemical environment of the female reproductive tract, making it hostile for sperm.
What are the different types of birth control pills?
The active ingredients in birth control pills are synthetic versions of the female hormones estrogen and progesterone. Combination oral contraceptives are birth control pills that contain both ingredients. There are some birth control pills that are progesterone-only pills. Sometimes referred to as "minipills," progestin-only pills are especially useful for women who cannot take estrogens. They are also suitable for women who are breastfeeding because they don't interfere with the production of milk.
The various brands of combination birth control pills generally come packaged in blister packs containing 21 or 28 tablets. After finishing the 21 day pack, there is a week without any pills when withdrawal bleeding occurs. This will be like a regular menstrual period but generally lighter. Then a new pack is started on the same day of the week as the start of the previous pack.
In the 28-day pack, typically 21 pills are active pills containing hormones and the other pills are "reminder" pills without hormones. Some reminder pills may contain iron. By taking reminder pills, a woman takes a pill each day, which can help maintain her birth control regimen. The progestin-only pills come in 28-day packs with all the pills being active containing hormone. With pills containing continuous hormone, there isn't any scheduled time of bleeding, but spotting or unexpected bleeding may occur.
It is possible to reduce the number of menstrual periods a woman has in a year or even to eliminate them all together. Since 2003, brands of birth control pills have been available in 84-day regimens for what's known as extended-cycle oral contraception. Women who use this method take an active pill every day for 12 weeks. Then they may stop or take a placebo for seven days, during which time they will have their period. Or they may continue to take an active pill for up to a year. Some brands of birth control pills sold for extended-cycle oral contraception conclude the regimen with seven active pills that contain a smaller dose of estrogen, which can have the effect of reducing the amount of bleeding that occurs during a period.
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