Does how much I weigh reduce the effectiveness of emergency birth control pills?

If your body mass index (BMI) is more than 30 — especially if you use levonorgestrel — emergency contraception may not be as effective, and you could be at risk of still being pregnant after taking the pill or pills. BMI is not as much of a concern when using ulipristal or the copper intrauterine device.

I have taken birth control pills for years and want to stop. Can I stop at any time or should I finish my 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 I get pregnant during the week of nonactive (placebo) pills?

Taking the nonactive pills doesn't put you at higher risk of unintended pregnancy. If you're taking birth control pills exactly as directed, they're about 99 percent effective at preventing pregnancy.

But if you miss 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, especially if you miss several pills during a cycle.

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 cancer risk?

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 the results aren't consistent. Most data shows that birth control pills don't increase your overall risk of cancer.

On the flip side, the birth control pill may decrease your risk of other types of cancer, including ovarian cancer and endometrial cancer.

Regarding breast cancer risk, some very early studies showed a link between pill use and breast cancer — likely due to the high estrogen dose found in contraceptive pills used in the 1970s. But, today's pills have a much lower estrogen dose, and more recent studies show no increase in breast cancer risk if you take birth control pills. Studies also have found no link between breast cancer risk and use of birth control pills in women who have a family history of breast cancer.

Do birth control pills affect cholesterol levels?

Birth control pills can affect your 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 your 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 another form of birth control.

Can women older than age 35 continue taking birth control pills?

If you're healthy and you don't smoke, you can continue taking birth control pills after age 35. However, birth control pills aren't recommended if you're 35 or older and you smoke because of the risk of cardiovascular disease. In that case, 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 (Rimactane). Rifampin does decrease the effectiveness of birth control pills in preventing ovulation, but this antibiotic isn't widely used today.

May 04, 2016 See more In-depth