Home HealthTopics Health Centers Reference Library Research
Join us on Facebook Join us on Facebook Share on Facebook
Print this pageEMail this page

Pregnancy

Oral Contraception (Birth Control Pills)

Birth Control PillsOral contraception is often referred to as "the pill". The pill is one of the most effective reversible methods of birth control. There are two basic types:

Both kinds of pills are intended to prevent pregnancy, and require a medical examination, doctor's prescription, and a follow-up visit. Listed below are some commonly asked questions about the pill.

  1. How does the pill work?
  2. How effective is the pill?
  3. What other benefits does the pill provide?
  4. What are the common side effects?
  5. What are the risks?
  6. Who should NOT take the pill?
  7. How long can I remain on the pill safely?
  8. Is it safe to take the pill while breastfeeding?
  9. What day should I begin taking the pill?
  10. What do I do if I miss a pill?

How does the pill work?

The pill is made of hormones like those made by a woman's ovaries--estrogen and progestin. Combination pills contain both hormones, "mini-pills" contain only progestin. Combination pills usually work by preventing a woman's ovaries from releasing eggs (ovulating). Mini-pills usually work by thickening the cervical mucus to keep sperm from joining with an egg, although combination pills do this as well.

How effective is the pill?

The pill is one of the most effective reversible methods of birth control. Reversible means that when or if you wish to become pregnant, you simply stop taking the pill. For every 100 women who use the pill, only 3 will become pregnant during the first year of typical use. Women who take the pill correctly every day (perfect use) have less than a 1% chance of getting pregnant. Typical antibiotics used for minor infections have never been shown to decrease the effectiveness of the pill. They may cause a woman to have some breakthrough bleeding, but is important to continue taking the pill. More potent antibiotics like those used to treat tuberculosis can reduce the effectiveness of the pill. If you are particularly concerned, you can use a back-up method like condoms until you finish the antibiotics and start a new month of contraception. The pill does not provide protection against sexually transmitted diseases (STDs) or HIV/AIDS.

Correct and consistent use of the pill increases your protection against pregnancy. You must take the pill every day and in the right order. It is very important not to skip pills, even if you have spotting or bleeding between periods or do not have vaginal intercourse very often. Taking the pill at the same time each day makes it more effective, and also helps you remember to stay on schedule. Pick a time of day that will be easy to remember.

What other benefits does the pill provide?

The pill has important benefits not related to contraception. Women who take the pill are more likely to have regular menstrual cycles (periods), less pain and blood flow during their periods, less anemia from heavy menstrual bleeding, less acne, lower rates of benign breast disorders/tumors, and fewer upper genital tract infections. Taking birth control pills can reduce your risks of ovarian and uterine cancer by up to 50% in those who take them for 1 or more years.

What are the common side effects?

Some of the more common side effects associated with birth control pills include breast tenderness, nausea, headaches, bloating, and bleeding between periods. These are not very common, but when they do occur they will usually go away within 1 to 3 months of continued use. Nausea can be reduced by taking the pill at bedtime. Bleeding and spotting between periods happens more often with mini-pills than combination pills. Often times women quit taking the pill when they have breakthrough bleeding, because they think the pill isn't working. Stopping the pill for this reason without a backup method of contraception is one of the more common reasons for an unplanned pregnancy while on the pill. Breakthrough bleeding and spotting in a woman who is taking the pill consistently isn't a sign that the pill is not effective in preventing pregnancy. Switching to a different brand of birth control pill can often solve the above side effects. You should talk to your doctor before stopping the pill if you are experiencing uncomfortable side effects.

What are the risks?

Serious problems do not occur very often, but pill users have a slightly greater chance of certain disorders than non-users. The most serious is the possibility of blood clots in the veins of the legs, lungs, heart, or brain. This is because estrogen in the combination pill increases the bodies ability to clot. The risk is still small. Non-pill users have a 10 in 100,000 chance of a spontaneous clot compared to 20-40 in 100,000 combination pill users. More importantly, the risk in pregnancy is greater yet at 60 in 100,000. An arterial clot causing a heart attack may happen, but the risk is only increased in women who are older than 35 and smoke. Birth control pill users of all ages are encouraged to stop smoking while on the pill.

Rarely, high blood pressure may develop in women who take the pill. The rise usually is slight, but it may worsen over time. Stopping the pill almost always brings blood pressure back to normal. Be sure to have your blood pressure checked after your first three months on the pill, and have it checked at least once a year after that.

Very rarely, liver tumors, gallstones, and jaundice (yellowing of the skin or eyes) occur in women who take the pill. Most experts agree that taking the pill does not increase the overall risk of developing breast cancer--no matter how long a woman takes the pill or even if she has a close relative with breast cancer. Serious problems usually have warning signs. Watch for them. If one occurs, report it to your clinician as soon as possible.

Warning signs include:

Who should NOT take the pill?

You should NOT take the pill if you:

If you have slightly high cholesterol or blood pressure, or have had diabetes, you should only take the pill under close medical supervision. Women with a history of migraine headaches may not be able to continue the pill if it makes the problem worse.

How long can I remain on the pill safely?

There is no limit to the amount of time a woman can safely remain on birth control pills. The length of time on birth control pills does not affect a woman's ability to become pregnant in the future.

Is it safe to take the pill while breastfeeding?

It is unlikely that the hormones contained in birth control pills will have any effect on your child. No harmful effects on breast milk have been reported with the progestin-only pills (mini-pills). However, small amounts of the hormones contained in combination pills are distributed into breast milk. The use of pills containing estrogen (the combination pill) has been reported to decrease milk production and milk protein and nitrogen content. However, these effects are not likely to be serious except in malnourished mothers. A few cases of harmful effects in infants breast-fed by mothers on combination pills have been reported, including jaundice and breast enlargement. Some doctors recommend the mini-pill to mothers who are concerned about a decrease in their milk production.

What day should I begin taking the pill?

Sunday Start Method

First-day Start Method

On the First-day start method, you take your first pill during the first 24 hours of your period. You are protected immediately against pregnancy, and do not need to use a back-up method of birth control.

What do I do if I miss a pill?

Below are some general guidelines for what to do if you miss a pill(s) and are not sure what to do. Talk to your health care provider for more specific instructions.

Use a back-up method anytime you have vaginal intercourse if you miss taking a pill.

If you forget ONE active combination pill:

If you forget TWO active combination pills in a row in the first two weeks:

If you forget TWO active combination pills in a row in the third week-or you forget THREE or more active combination pills in a row during the first three weeks, do the following:

FOR "SUNDAY STARTERS": Take one active pill every day until the next Sunday. Throw away the rest of the pack and start a new pack the same day (Sunday). Use a back-up method for seven days after the pills are skipped. You may not have your period this month, but this is expected. Call your clinician if you do not get your period two months in a row.

FOR "FIRST-DAY STARTERS": Throw away the rest of the pack. Start a new pack the same day. Use a back-up method for seven days after the pills are skipped. You may not have your period this month, but this is expected. Call your clinician if you do not get your period two months in a row.

If you forget ANY of the seven reminder pills in the fourth week:

If you forget EVEN ONE progestin-only pill:

*Some of the information contained on this page was abstracted from fact sheets developed by Planned Parenthood Federation of America

Before getting pregnant - What you should know

For more information:

Go to the Pregnancy health topic, where you can:

This article is a NetWellness exclusive.

Last Reviewed: Jan 18, 2007

Thomas  A deHoop, MD Thomas A deHoop, MD
Formerly Associate Professor of Clinical Obstetrics and Gynecology
Director, Medical Student Education
No longer associated