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 to 99 percent effective at preventing pregnancy.

If, however, you've missed a pill — or several 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?

Many women think so. But studies have shown that the effect of the birth control pill on weight is small — if it exists at all. Instead, you may be retaining more fluid, which can make you feel as if you've put on weight, particularly in your breasts, hips and thighs. The estrogen in birth control pills does affect fat (adipose) cells, making them larger but not more numerous.

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. While some studies have shown a link between pill use and breast cancer, more-recent studies do not show an increased risk of breast cancer with the pill. If you're concerned about your risk of breast cancer, talk with your health care provider about whether the pill is the right contraceptive for you.

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. Birth control pills with more 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 slightly increase blood pressure. If you take birth control pills, have your blood pressure checked regularly. If you already have high blood pressure, talk with your doctor about whether you should consider an alternative form of birth control.

Can women over age 35 continue taking birth control pills?

Although women older than age 35 used to be told to stop taking birth control pills, these limits no longer apply to healthy, nonsmoking women. However, birth control pills aren't recommended for women older than age 35 who smoke because of 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 birth control pills.

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 used widely today.

May. 21, 2013 See more In-depth