Birth control pills are prescription medications commonly used by women as a form of contraception. Also known as “the pill,” they contain the synthetic female hormones estrogen and progestin (a synthetic form of progesterone). Used in combination or alone, these hormones prevent pregnancy by:

• Preventing ovulation
  
  
• Keeping the mucus in the cervix thick so sperm cannot penetrate it
  
  
• Preventing a fertilized egg from implanting in the endometrium (uterine lining)

There are two main types of birth control pills – combined birth control pills and progestin-only pills. Combined birth control pills contain both estrogen and progestin. Progestin-only pills (POPs), or “mini-pills,” contain only progestin. To use the medication, one pill is taken at the same time every day for 21 days, 28 or 91 days. When used correctly, birth control pills have an effectiveness rate of more than 99 percent. This effectiveness, however, may be reduced by some medications, including certain antibiotics, and improper use.

Although they are most commonly prescribed to prevent pregnancy, birth control pills are also used to treat a variety of menstrual disorders including amenorrhea (absence of menstruation), dysmenorrhea (abnormally painful menstruation) and hypermenorrhea (abnormally heavy menstrual bleeding). They may also be prescribed to treat a number of other conditions, including  polycystic ovarian syndrome (PCOS), hirsutism (abnormal hair growth) and endometriosis. In addition, birth control pills may be taken to regulate irregular menstrual cycles and to help in the transitional period prior to menopause.

In addition to preventing pregnancy and treating various medical conditions, birth control pills also offer women a number of significant health benefits, including a decreased risk of colorectal, ovarian and endometrial cancers.

Although the pill is safe for most women to take, women with certain conditions may be advised against it. Women who have blood clots, certain cancers, a history of heart attack, stroke or liver problems and those who are or may be pregnant should not take birth control pills. Women taking the pill are also urged not to smoke because smoking may increase the risk of heart attacks, strokes and blood clots.

There are more than 40 brands of birth control pills available in the United States. Each contains slightly different forms of hormones or doses and is taken differently. A woman’s physician, usually her obstetrician-gynecologist (ObGyn), can determine which type of pill might be best for the woman based on a number of factors. Women should be familiar with the brand of pills they are taking, carefully follow all usage instructions and report any medical problems they encounter. Changing the brand or dosage may alleviate the side effects while still providing effective contraception.