Dr. Oz

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In my years as a heart surgeon, I've seen far too many patients who suffered strokes because they weren't aware of the causes. According to a recent report published by the American Heart Association, one in five women can't name a single warning sign. However, each year roughly 55,000 more women than men have strokes, which kill nearly twice as many women as breast cancer. The good news: Strokes can be preventable—but only if you're aware of the dangers.
Preeclampsia

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Risk Factor #1: Preeclampsia
After the 20th week of pregnancy, some women develop preeclampsia, a disorder characterized by a spike in blood pressure along with higher protein levels in urine—both of which increase your chance of stroke. Though preeclampsia typically goes away within six weeks of giving birth, a history of the condition has been found to almost double the risk of stroke later in life. If you have high blood pressure before pregnancy, your odds of developing preeclampsia are about 25 percent, so make sure you ask your doctor for a screening. And have your BP checked six months to a year postpartum to confirm that it's dropped back within a healthy range.
Migraines

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Risk Factor #2: Migraines
These skull-busting headaches—which affect three to four times more women than men—may double your risk of ischemic stroke (which results when a clot blocks a blood vessel leading to the brain), according to a report in The American Journal of Medicine. Researchers hypothesize that people with migraines have impaired blood vessel function, making them more susceptible to stroke. While there's currently no cure for migraines, you can take proactive steps to lower your overall stroke risk by exercising, eating a healthy diet and not smoking.
Birth Control Pills

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Risk Factor #3: Birth Control Pills
Several studies have shown that women who take oral contraceptives may be more than twice as likely to have a stroke as those who don't. (Hormones in the pills may increase the risk of blood clots and raise blood pressure.) It's rare for the pill to cause a stroke in healthy young women, but if you already have other risk factors, your odds of developing a dangerous clot shoot up considerably. In fact, one study of women ages 15 to 49 found that smokers who experienced migraines with auras (flashing lights or blind spots) and were on the pill were seven times more likely to have a stroke compared with those with migraines who didn't smoke or take the pill.
Irregular Heartbeat

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Risk Factor #4: Irregular Heartbeat
When the upper chambers of the heart beat rapidly and out of sync with the bottom chambers—known as atrial fibrillation (or A-fib)—blood can begin to pool in the heart's upper chambers, increasing the risk that clots will form. You can screen for A-fib at home with a simple 60-second pulse check. If you notice that the beats seem uneven and faster than normal, consult your doctor; she can perform more tests to determine whether you have the condition and recommend treatment to reset your heart rate or rhythm.

Mehmet Oz, MD, is the host of The Dr. Oz Show (weekdays; check local listings).