There are three different types of birth control pills, also known as oral contraceptives, on the market today: the combination pill, the mini-pill and the emergency contraceptive pill.

Combination pill
This pill, which contains the hormones estrogen and progestin, is the most widely prescribed. It works by suppressing ovulation each month. By thinning the uterine lining and changing the consistency of the mucus in a woman's cervix, it also makes it harder for sperm to move into contact with an egg.

There are different formulations. Some require a 21-day regimen followed by one week of placebo tablets. Others vary the dose of estrogen and/or progestin that a woman gets throughout her cycle, or add five additional estrogen pills at the end of the 21-day cycle. But all of today's pills contain far less estrogen than their older counterparts.

In 2007, the FDA approved Lybrel, the first continuous use birth control pill. It is a multiphasic pill (containing varying levels of estrogen and progestin designed to be taken at specific times throughout the entire pill-taking schedule) and comes in a 28-day pack. This product is designed to be taken continuously, which means you won't have a period, although you may have some spotting or breakthrough bleeding.

There are no long-term fertility effects associated with birth control use.
One caveat: Some medications, including antibiotics, anticonvulsants and herbal products like Saint Johnswort which may help relieve mild depression can reduce the effectiveness of the pill.

Benefits
In addition to preventing pregnancy, birth control pills can:

  • Regulate, shorten or eliminate a woman's menstrual cycle   
  • Decrease severe cramping and heavy bleeding
  • Reduce anemia
  • Lower ovarian, uterine (endometrial) and colorectal cancer risk
  • Reduce the development of ovarian cysts  
  • Reduce the risk of ectopic (tubal) pregnancy
  • Decrease benign breast disease   
  • Minimize perimenopausal symptoms, such as irregular menstrual bleeding
  • Diminish acne

   

Who shouldn't take the pill
Women with certain health conditions may not be able to use birth control pills. These include:

  • Heart disease or stroke
  • Liver disease
  • Blood clots in the deep veins or lung
  • Breast cancer
  • Severe or uncontrolled diabetes
  • Smokers 35 or older (can result in heart attack or stroke)
  • Women of any age prone to migraines with "aura"—blurred vision, temporary loss of vision or seeing flashing lights—and women over age 35 who get migraines (with or without aura)
  • Severe hypertension (substantially higher relative risk of ischemic (blood clot in the brain) and hemorrhagic (blood vessel rupture in the brain) strokes)

 

Other risks
Some women worry that the pill may increase their risk for breast cancer, but the evidence remains unclear, notes the American Cancer Society. Studies have found a slightly higher risk of breast cancer in women who take birth control pills. However, women who stopped using the pill 10 or more years ago do not show an increased risk. Discuss the risks and benefits of birth control pills with your health care professional.

There is some evidence that long-term use of the pill may increase the risk of cancer of the cervix (the narrow, lower portion of the uterus). There is also some evidence that the pill may increase the risk of certain benign (noncancerous) liver tumors. However, the actual risk and role of birth control pills in both these cancers is unclear.

Possible side effects
Nausea, breast tenderness and bleeding are the most common side effects of all birth control pills. Most side effects decrease or disappear after three months of continuous use. Switching to another formulation can also relieve side effects.

Saint Johnswort This herbal product that may help relieve mild depression can interfere with the effectiveness of certain drugs, including oral contraceptives. According to Swedish scientists, several women who took Saint Johnswort while on the pill have gotten pregnant.
Antibiotics To resolve a longstanding controversy, the American Medical Association recently reviewed studies and found that yes, antibiotics do occasionally lessen the effectiveness of oral contraceptives. The AMA recommends that if you have experienced breakthrough bleeding or unplanned pregnancy in the past while using both birth-control pills and antibiotics, you should err on the side of safety and use another method of contraception while taking antibiotics.

"Mini Pill"
A single, progestin-only pill is taken every day. These pills work by reducing and thickening cervical mucus to prevent sperm from reaching the egg. They also keep the uterine lining from thickening, which prevents a fertilized egg from implanting. They are not as effective in preventing pregnancy as combination pills and must be taken exactly on time, everyday.

However, the progestin-only pill may be an option if you want to use oral contraception, but you're breast-feeding or experience uncomfortable side effects from estrogen, such as headaches.

The main side effect from mini-pills is menstrual irregularity; you may not have any bleeding for months or you may have some spotting between periods.

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Emergency Contraception
Commonly called "the morning after pill," emergency contraception pills are used after unprotected intercourse or contraceptive failure. To be the most effective, the pills should be started as soon as possible after up to 72 hours after unprotected intercourse, although some data suggests it may be effective up to 120 hours. Following the first dose of medication, a second dose must be taken within 12 hours.

Side effects and risks
Emergency contraceptive pills should not be used regularly as birth control because they can disrupt your menstrual cycle. They are also not 100 percent effective and can cause side effects such as nausea and vomiting, headaches, breast tenderness, dizziness and bloating. Emergency contraceptive pills that contain only progestin cause fewer side effects.