Blood Clots and the Pill

Kelly Anne Spratt, D.O., Director of Women's Cardiovascular Health at the University of Pennsylvania Presbyterian Medical Center, answers your questions.

Q. The literature that comes with my oral contraceptives warns about sudden pain in the calf as a possible indication of a blood clot forming. As a result, every time I feel the slightest pain in my calves, I worry incessantly until it goes away. I suspect that at least some of the time, these pains are exercise-related. How worried should I be? How do I know when to ask my husband to call an ambulance because I indeed have a blood clot rampaging toward my brain? I have been on a low-dose birth-control pill for five years; I'm 30 years old.

A. First, relax and take a deep breath! Although the package insert for oral contraceptives can be frightening indeed, so is the list of possible side effects for all medications, including aspirin (a slim chance of bleeding in the brain) or Tylenol (has been known to cause liver problems). Yet you likely have taken these without thinking of these remote, but possible side effects. Blood clots in the legs are a rare but possible side effect in women on the Pill. Mostly they are seen in women with a genetic predisposition to clotting. If you were one of these women, you would probably already have had a clot after 5 years on the pill. Women who smoke, particularly those over age 35, also have a higher risk of clots.

If this is really upsetting you to this degree, ask yourself why you are so incessant about this. Perhaps you do not want to be on the pill, which should prompt a discussion with your husband about other options for birth control such as condoms or a diaphragm. But remember, these also will come with warnings about side effects regarding latex allergy and increased risk of urinary tract infections. There is no simple answer! As far as when to call for help, know the symptoms of a clot, which are more than simple pain (your aches probably are due to exercise) and include swelling of the calf and inability to move your toes forward without excruciating pain. Blood clots in your legs do not go to your brain since in most persons the lungs filter out the clots before they ever get to the heart, let alone the brain.

Instead of obsessing about a remote possibility, try to focus on the health benefits of the pill, including not only a high success rate for contraception but also a 50 percent reduction in ovarian cancer risk and a higher degree of bone mass at the time of menopause leading to a marked decrease in risk of osteoporosis.