Birth Control Pill Basics

The pill is effective and easy to use, making it the most widely used form of reversible birth control in the U.S. When used correctly, birth control pills (oral contraceptives) are more than 99 percent effective in preventing pregnancy.

How the pill works

Birth control pills contain hormones that help prevent pregnancy. The pill works in three different ways by:

• Preventing ovulation. Ovulation is when the ovary releases an egg. Hormones stop the egg from leaving the ovary so it cannot be fertilized by the sperm
• Blocking fertilization. Hormones cause the cervical mucus to thicken. This helps block the sperm from reaching the egg
• Thinning the lining of the uterine wall. This keeps any egg that may have been fertilized from attaching to the uterine wall. A pregnancy will not occur if the egg doesn't implant

The pill is a temporary type of birth control. It can be stopped at any time without affecting fertility. In fact, it's often possible to get pregnant the first cycle you're off birth control pills.

Types of pills

Birth control pills are available by prescription only. The pill contains hormones that prevent pregnancy:

• Combination pills are made up of estrogen and progestin
• Progestin-only pills contain no estrogen

Pills also vary in how often you have your period. With most birth control pills, you will have your period once every cycle (once every four weeks). If you take continuous dosing or extended use birth control pills, you may only get your period once every three months for a total of four periods a year.

Your pill pack

Birth control pills come in packs of 21, 28 or 91 tablets. If your pack has:

• 21 pills. Take one pill each day for 21 days. Then you do not take any pills for seven days. You start the next pack of pills exactly one week after your last pack has finished. During the week off the pill, you will have your period
• 28 pills (combination pills). Take one pill each day for 28 days. Start the new pack the day after you finish your old pack. The first 21 pills in the pack are "active" - meaning they contain hormones - and the last seven are placebo pills. You will have your period the week of the placebo pills. These placebos serve as reminders to reinforce your habit of taking the pill each day. They can be skipped if you want. But if you skip them, make sure to start the new pack of pills exactly one week after taking your last active pill
• 28 pills (progestin-only). Take one pill a day for 28 days. All pills in the pack are active, so you must not miss a pill
• 91 pills (continuous dosing or extended use pills). Take one pill each day for 91 days. The first 84 pills are active and the last seven are placebos. You will have your period during the week of the placebo pills

Pros and cons of the pill

Pros:

• Very effective pregnancy prevention when taken correctly
• You don't need to worry about birth control before or during sex
• Lessens menstrual cramp pain. Periods will be regular, lighter and will not last as long
• Some studies show that the pill lowers your risk of certain health problems, although more research is needed. The pill may help reduce:
  • Ovarian and endometrial cancer
  • Ovarian cysts
  • Pelvic inflammatory disease (progestin pills only)
  • Ectopic pregnancy (pregnancy that grows outside the uterus)
  • Iron-deficiency anemia (low blood iron)
  • Bone loss
  • Noncancerous breast disease
  • Acne
  • Migraines and depression (continuous pills)

Cons:

• The pill must be taken at about the same time every day. If you miss a pill or take it at the wrong time, it may not work and you could get pregnant. This burden is reason enough for many women to choose other methods of contraception. You may find it helpful to set an alarm on your cell phone or watch as a reminder to take the pill
• It does not protect against sexually transmitted diseases (STDs). Unless you are in a monogamous relationship and both you and your partner have tested negative for STDs, you should not use the pill as your sole method of contraception. Use a barrier method of birth control - like condoms - along with the pill to help prevent STDs
• Some women have side effects, though they usually only last for the first two to three months you're on the pill. These are:
  • Nausea
  • Breast tenderness
  • Bleeding between periods, called "breakthrough bleeding" (more common with progestin-only pills)
  • Dizziness
  • Headache
  • Depression
  • Anxiety
• Serious side effects are rare, but can occur:
  • Heart attack
  • Stroke
  • Blood clot in the heart, lungs, legs or brain
  • High blood pressure
  • Liver tumors
  • Gallstones
  • Jaundice (yellowing of the eyes and skin)
• The pill is not safe for all women to take. The American College of Obstetricians and Gynecologists says the following women should not use certain types of birth control pills:
  • Heavy smokers or those who smoke and are over age 35
  • Those with uncontrolled high blood pressure
  • Those with a very high cholesterol (LDL or "bad" cholesterol over 160 mg/dL)
  • Those who have a history of stroke, heart disease or blood clots
  • Those who have certain liver conditions
  • Those with abnormal vaginal bleeding
  • Those with diabetes and other risk factors, including: women who are age 35 years or older; have vascular (blood vessel) problems, heart problems or other end-organ damage; or who smoke
  • Those with breast cancer
  • Those with certain types of migraines

Some other women should also consider different forms of birth control. Talk to your doctor about your specific risk.