Birth Control Pills

What hormones are in birth control pills?

Birth control pills (also called oral contraceptives or hormonal contraceptives, BCPs for short) are the most commonly used form of birth control in the US. Most common BCPs contain a combination of two hormones, estrogen and progestin (although some pills contain only progestin).

Most women take low-dose birth control pills, which have 50 micrograms or less of estrogen. Modern birth control pills contain 20 to 50 micrograms of estrogen—more than 50 micrograms is considered “high-dose.” Older birth control pills contained up to 5 times as much estrogen and 10 times as much progestin as modern pills. Because studies found that these older pills caused serious complications including stroke, heart attack, and blood clots in the lungs (pulmonary embolism), the amounts of hormones were reduced.

Do birth control pills affect stroke risk?

Using birth control pills raises your risk of stroke a small but significant amount. In healthy young women (non-smokers under age 35 who do not have high blood pressure), the overall risk is low.

There is controversy over whether the modern low-dose pill (<50 micrograms of estrogen) increases the risk of stroke, but if it does, the increase is very small. In women younger than 35 who do not smoke or have high blood pressure, the risk of stroke is 10 per 100,000 women, and this only increases to about 13 per 100,000 in women taking birth control pills. Women who use high-dose pills (>50 micrograms of estrogen) are more likely to have a stroke because the high hormone doses increase the chances of developing blood clots. A Dutch study looking at the risks associated with older versus newer generation birth control pills found that the risk of stroke in women using the newer (third-generation) oral contraceptives (containing the hormones desogestrel or gestodene) was not different from that in women using the older (second-generation) oral contraceptives (containing levonorgestrel).

What risk factors increase the likelihood of stroke with birth control pills?

In women with certain risk factors, taking birth control pills can increase the risk of stroke and heart disease. You may want to consider an alternative method of birth control if you:

  • Are a smoker
  • Have high blood pressure
  • Are overweight or obese
  • Have diabetes
  • Experience regular migraine headaches
  • Have been diagnosed with heart disease, stroke, or blood clots
  • Have a family history of heart disease or stroke

The combination of smoking and birth control pills is dangerous and greatly increases a woman’s risk of serious cardiovascular problems such as blood clots that can lead to stroke. Birth control pills alone slightly increase your risk of stroke, but when combined with smoking they increase your chances of having a stroke by as much as 40 times, particularly in women older than 35.

Blood levels of sugar (glucose) sometimes change dramatically in women who take birth control pills. If you are diabetic or have a close relative who is, you should have your blood sugar monitored closely when starting the pill. See the section on Diabetes and Stroke Risk for more information.

Women who have a history of migraines with aura – visual symptoms such as blurred vision, intermittent loss of vision, flashing lights or zigzag lines – have a slightly increased risk of stroke compared with women who do not have migraines. There is some evidence that women who have migraines with aura and who also take birth control pills are at an even greater risk of stroke, but potentially only in the presence of other risk factors, especially smoking. Some recent studies reported that women who have migraines with aura who also take birth control pills and smoke cigarettes are 7 times more likely to have a stroke than women with migraines who do not smoke or take BCPs.

If you have had a heart attack or a stroke or if you have a history of cardiovascular disease or blood clots, hormonal contraceptives may not be a safe option for you. Be sure to discuss your medical history with your health care provider, including whether you have taken high-dose birth control pills in the past, before taking hormonal contraceptives.

Do birth control pills affect risk factors for stroke?

High blood pressure is an important risk factor for stroke, and taking oral contraceptives slightly raises blood pressure, causing some women to develop high blood pressure. If you take the pill or wear the patch, you should have your blood pressure checked at least once a year. High blood pressure occurs 2 to 3 times more often in women on the pill than in women who do not take it – especially in women who are obese, are older than 35, have mild kidney disease or a family history of high blood pressure, or have had high blood pressure during pregnancy. If you use birth control pills and your blood pressure becomes high, you should talk to your health care provider about switching to a different method of birth control. Once you stop taking the pill, your blood pressure will return to normal in 3 to 6 months. If you’ve had high blood pressure in the past but it is under control with high blood pressure medication, you may still be able to take the pill, but your blood pressure will need to be closely monitored.

A recent report also raises the possibility that birth control pills may contribute to atherosclerosis (hardening of the arteries) when taken over a very long period. At the 2007 meeting of the American Heart Association, researchers presented an observational study of 1301 women that showed a 20% to 30% increased risk of clogged arteries for every 10 years of BCP use among women 35 to 55 years old.


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