Birth control pill FAQ: Benefits, risks and choices

If you use the birth control pill — that is, an oral contraceptive — you're probably happy with its convenience and reliability. Still, you may have many questions about the potential effects of birth control pills on your overall health. Here's what Mayo Clinic specialists have to say about women's health and oral contraceptive use.
How do pills that eliminate some or all your periods differ from other birth control pills?
Traditional birth control pills make your reproductive system mimic a regular 28-day monthly cycle. For the first 21 days, you take active pills containing reproductive hormones. For the last seven days, you take a placebo. While you're taking the placebo pills, you bleed vaginally, as if you were having a regular menstrual period.
By contrast, extended-cycle birth control pills contain active hormones for every day of the month. The newest extended-cycle regimen, Lybrel, is a low-dose pill that's designed to be taken continuously for one year, with no breaks for hormone-free intervals. Lybrel is meant to suppress all menstrual bleeding.
Two other specially designed, extended-cycle pill regimens — Seasonale and Seasonique — are also currently on the market. With both pills, you take active hormone pills every day for three months, then you take one week of placebo pills (Seasonale) or low-dose estrogen pills (Seasonique). You'll experience menstrual bleeding during that week.
Can you use ordinary birth control pills continuously to prevent having a period?
It's possible to prevent your period with continuous use of any birth control pill. This means skipping the placebo pills and starting right away on a new pack. Some evidence suggests an advantage to this type of pill regimen. By continuously taking the pill, you prevent hormonal fluctuations that are responsible for bleeding, cramping, headaches and other discomforts associated with getting your period. However, you're at greater risk of breakthrough bleeding — bleeding between periods. Continuous use of your birth control pills works best if you're taking a monophasic pill — with the same hormone dose in the three weeks of active pills. If you're taking a triphasic pill — with a different hormone dose each week of the active pill phase — using them continuously carries a much higher rate of breakthrough bleeding.
You may find continuous use of birth control pills a convenient way to avoid having your period during an important occasion or trip. Taking a monthly regimen birth control pill continuously is fine for about three months, but then you should plan on taking the placebo pills so that you'll have a menstrual cycle.

If you plan to have a baby, how soon after stopping the birth control pill can you conceive?
One of the advantages of the birth control pill is that it's quickly reversible. After you stop taking the pill, you may have only a two-week delay before you ovulate again. Your period would follow about four to six weeks after you take the last pill.
Once ovulation resumes, you can become pregnant. If this happens during your first cycle off the pill, you may not have a period at all. However, although possible, this scenario isn't likely.
Is there an advantage to waiting a few months after stopping the pill before trying to conceive?
For the purpose of dating the pregnancy — estimating when you ovulated and when your baby is due — it's somewhat advantageous to have at least one normal period before conceiving.
In the past, doctors had concerns that if you conceived immediately after stopping the pill, you had a higher risk of miscarriage. However, these concerns have proved to be largely unfounded.
If you plan to wait a few months, use a backup form of birth control while your menstrual cycles get back to normal.
What happens if you stop taking the birth control pill but your period doesn't resume?
When you stop using the birth control pill but you don't get a period for several months, you may have what's known as post-pill amenorrhea. The pill prevents your body from making hormones involved in ovulation and menstruation. When you stop taking the pill, it can take some time for your body to return to normal production of these hormones.
Typically, your period should start again within three months after you stop taking the pill. Most women ovulate promptly and have a period within four to six weeks. But some women, especially those who took the pill to regulate their menstrual cycles, may not have a period for many months.
If you don't have a period within three months, take a pregnancy test to make sure you're not pregnant. If after six months you still don't have a period, see your doctor.
Will a pregnancy test be accurate if you're taking the birth control pill?
You can get accurate results from a pregnancy test while you're on the pill. Pregnancy tests work by measuring a specific pregnancy-related hormone — human chorionic gonadotropin (HCG) — in your blood or urine. The active ingredients in birth control pills don't affect how a pregnancy test measures the level of HCG in your system.
What happens if you take birth control pills while you're pregnant?
If you continued taking your birth control pill because you didn't realize you were pregnant, don't be alarmed. Despite years of this accident happening, there's very little evidence that exposure to the hormones in birth control pills causes birth defects.
Still, the birth control pill is a potent estrogen. Lessons learned from women who took diethylstilbestrol — a synthetic estrogen that was later linked with cancer — to prevent miscarriage in early pregnancy suggest that such exposure should be minimized.
Once you learn that you're pregnant, stop taking the birth control pill.
Can you use several birth control pills at once for emergency contraception?
It's possible to use standard estrogen-progestin birth control pills for emergency contraception, but check with your doctor for the proper dose and timing of the pills.
There is a special type of contraceptive pill that's specifically designed to keep you from becoming pregnant if you've had unprotected vaginal intercourse. An emergency contraception pill (Plan B) — also called the "morning-after pill" — contains a higher dose of progestin than is found in other birth control pills and is available over-the-counter for women age 18 and older. Otherwise, check with your doctor, local emergency room or Planned Parenthood clinic if you're in need of emergency contraception.
If you've been taking birth control pills for many years and decide to stop, can you stop at any time or should you finish your current pill packet?
In terms of your overall health, it makes little difference when you stop taking the pill. When you finally do stop the pill, you can expect some bleeding, which may change the rhythm of your menstrual cycle. But you can stop at any time.
Can you get pregnant during the week that you take the nonactive (placebo) pills?
Taking the nonactive pills doesn't put you at higher risk of unintended pregnancy. If you're taking your birth control pills exactly as directed, they're 98 percent to 99 percent effective at preventing pregnancy.
If, however, you've missed a dose — or several doses — of your birth control pills during a cycle, you might be at higher risk of unintended pregnancy during that cycle. To be safe, use a backup form of contraception, such as a condom.
Do birth control pills cause weight gain?
Women often blame the birth control pill for weight gain. But studies have shown that the effect of the birth control pill on weight is small — if it exists at all.
However, the way the hormones in birth control pills act on tissues in your breasts, hips and thighs can make you feel as if you've gained weight. This is usually due to fluid retention and not increased body mass or fat. Estrogen in birth control pills directly affects fat (adipose) cells, making them larger, but not greater in number.
In very rare circumstances women may add muscle, which can add weight, when taking the pill. This is due to the slight male-sex-hormone effect that the pill may have on some women.
But no matter if pill-related weight gain is perceived or real, many women find this side effect undesirable. Taking pills with a low dose of estrogen may diminish these effects, but you may also experience a greater risk of spotting between periods.
How do birth control pills affect your risk of cancer?
Scientific evidence suggests using birth control pills for longer periods of time increases your risk of some cancers, such as cervical cancer and liver cancer, but it also decreases your risk of other types of cancer, including ovarian cancer and endometrial cancer.
The effect of birth control pills on breast cancer risk isn't quite clear. However, some studies do show a link between pill use and breast cancer. Key factors seem to be how many years you take the pill and how recently you last used the pill. In one study, use of birth control pills led to a higher risk of premenopausal breast cancer in women who took the pill for four or more years before having a baby. Other evidence suggests that 10 or more years after you stop taking the pill, your breast cancer risk returns to the same level as if you had never taken birth control pills.
Do birth control pills affect cholesterol levels?
Birth control pills can affect cholesterol levels. How much of an effect depends on the type of pill you're taking and what concentration of estrogen or progestin it contains.
The estrogen in birth control pills causes an increase in high-density lipoprotein (HDL) cholesterol levels (the "good" cholesterol), a decrease in low-density lipoprotein (LDL) cholesterol levels (the "bad" cholesterol) and an increase in your total cholesterol and triglyceride levels. Progestin in birth control pills has the opposite effect.
Birth control pills with a greater concentration of estrogen can have a slightly beneficial overall effect on your blood lipid levels. In general, though, the changes aren't significant and don't affect your overall health.
Do birth control pills affect blood pressure?
Birth control pills may increase blood pressure. The risk of high blood pressure in women who take birth control pills also increases with age and the duration of use.
If you take birth control pills, have your blood pressure checked regularly. If you already have high blood pressure, consider an alternative form of birth control. If you do choose to take the pill, have your blood pressure closely monitored by your doctor.
If you develop high blood pressure while taking the pill, give serious thought to switching to another form of contraception.
What's the risk of smoking if you're over age 35 and taking birth control pills?
Birth control pills aren't recommended for women over age 35 who smoke because it increases the risk of cardiovascular disease. If you're 35 or older, and you smoke, you need to quit smoking before you can safely continue using your birth control pill.
Can antibiotics decrease the effectiveness of birth control pills?
The effects of antibiotics on birth control pills may be overstated — except in the case of one antibiotic, rifampin. Studies clearly show that rifampin decreases the effectiveness of birth control pills in preventing ovulation. However, rifampin isn't a widely used antibiotic. Chances are you wouldn't be taking it unless you had tuberculosis or had tested positive for the disease.
Hypothetically speaking, other antibiotics, particularly penicillin and tetracycline derivatives, could impair the effectiveness of birth control pills. However, no large studies have proved such an effect.
Researchers can't rule out the possibility that a small percentage of women may experience decreased effectiveness of birth control pills while taking an antibiotic. And if you're taking a newer, extremely low-dose oral contraceptive, you could be more susceptible to these potential effects from antibiotics. If you're concerned, consider using a barrier method of contraception for the duration of your antibiotic prescription.
Do birth control pills prevent or delay menopause?
A woman still goes through menopause even if she is taking birth control pills. But she may not know it.
Menopause occurs naturally when your ovaries stop making estrogen and progesterone. Eventually your menstrual periods stop, and you can no longer become pregnant. Signs and symptoms of decreased production of estrogen and progesterone include hot flashes, sleep disturbances and vaginal dryness.
A menopausal woman taking birth control pills continues to get enough estrogen and progestin from the pills and will not realize her ovaries are no longer making these hormones. Her periods will continue, although she can no longer get pregnant. Menstruation occurs during the placebo week of the pill regimen. And she may have no symptoms of menopause because the pill continues to deliver more than adequate amounts of estrogen and progestin.
If you are taking the pill and are older than age 50, consider stopping oral contraceptive use. Discuss with your doctor how you can determine whether menopause has occurred and what alternatives there are for contraception if you still need it. When you no longer need contraception, hormone therapy is a better option for managing uncomfortable menopausal vasomotor symptoms, including hot flashes and night sweats.