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Birth control pill FAQ: Benefits, risks and choices

How are pills that delay your period different from regular birth control pills? Does the pill cause weight gain? Here are the answers.

By Mayo Clinic staff

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 the birth control pill on your overall health.

How do pills that delay or eliminate your periods differ from other birth control pills?

Traditional birth control pills 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 placebos. 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 first extended-cycle pill regimens introduced provide active hormone pills every day for three months, then one week of placebo pills (Seasonale) or low-dose estrogen pills (Seasonique, LoSeasonique). You'll experience menstrual bleeding during that week. A newer extended-cycle regimen is designed to be taken continuously for one year (Lybrel). It's meant to suppress all menstrual bleeding.

Some evidence suggests an advantage to this type of 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. Unscheduled bleeding and spotting often occur during the first few months. It typically goes away with continued use, but some women do continue to have unscheduled bleeding with continuous use of pills.

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. 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.

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, but with continuous use of the pill you may develop breakthrough bleeding and then you should take 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?

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.

Is there an advantage to waiting a few months after stopping the pill before trying to conceive?

If you have at least one normal period before conceiving, it will be somewhat easier to estimate when you ovulated and when your baby is due.

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?

If 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. 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 and then 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. 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 are two types of pills specifically designed to keep you from becoming pregnant if you've had unprotected vaginal intercourse. These medications are sometimes referred to as the "morning-after pill." Levonorgestrel (Plan B One-Step, Next Choice) is available over-the-counter for women age 17 and older. It's available at drugstores, as well as health clinics and Planned Parenthood. Ulipristal acetate (Ella) also is approved for emergency contraception. It's available only by prescription.

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• See Also

Hand Scheduled
Section Focus
• Birth control pills: OK to take indefinitely?
• Seasonale: Is breakthrough bleeding more common?
• Delaying your period with birth control pills
• Choosing a birth control pill
• Minipill (progestin-only birth control pill)
• Combination birth control pills
• Birth control pills for acne?
• Birth control pills: Harmful in early pregnancy?

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