If a pregnant woman were to complain of chest pain, my first thought would be that she's a young woman and almost certainly couldn't be having a heart attack. After all, women's levels of estrogen tend to protect them from heart attacks until after menopause, when estrogen levels go down.

Much to my surprise, a study from Duke found that pregnant women had heart attacks three to four times more often than women of the same age who weren't pregnant.

The risk of a heart attack during pregnancy, the study said, was dramatically higher in women over the age of 35. Other risk factors for a heart attack were diabetes, high blood pressure, an elevated blood platelet count, and cigarette smoking (even in women who had stopped smoking as soon as they knew they were pregnant).

Because blood platelets can trigger a blood clot, and blood tends to clot more readily during pregnancy, it's understandable that an elevated platelet count could increase the likelihood of a blood-flow-stopping clot in a coronary artery.

In the study, cardiac catheterization, which involves use of X-ray equipment, was carried out in fewer than half of the pregnant women who suffered a heart attack, presumably because their doctors were afraid of radiation damage to the fetus. Interventions with angioplasty or thrombolytic (clot-busting) therapy were also relatively uncommon.

A heart attack is still a rare event during pregnancy, but certainly one can occur in older women and those with other risk factors. Pregnant women and their families need to pay attention to symptoms suggestive of a heart attack in order to get swift and proper treatment.