A European study released on Tuesday has raised new concerns about the safety of women's long-term use of the birth control pill, suggesting increased risk of heart attack or stroke.
Women who had used oral contraceptives were more likely than those who did not take the pill to have a buildup of plaque in their arteries, the researchers told an American Heart Association meeting.
"The main concern is if you have higher plaque levels that you might develop a clot on one of these plaques and have a stroke or a myocardial infarction (heart attack) or sudden cardiac death," Dr. Ernst Rietzschel of Ghent University in Belgium, who led the research, told reporters.
"That's the main risk with having plaque, with having atherosclerosis."
Rietzschel's team studied 1,301 women ages 35 to 55.
Of them, 81 percent had used the pill, for an average of 13 years. The researchers saw a rise of 20 to 30 percent in arterial plaque in two big arteries -- the carotid in the neck and the femoral in the leg -- for each decade of use.
The researchers measured plaque levels using a technique called vascular echography.
In atherosclerosis, there is a hardening and narrowing of the arteries caused by the slow buildup of plaque, made up of fat, cholesterol, calcium and other material, on the inside of artery walls.
Rietzschel said he did not think the findings should trigger alarms about the safety of the pill.
"Bottom line -- don't discontinue your pill suddenly. Don't panic. Don't call your gynecologist tomorrow morning," Rietzschel said.
Other steps can be taken to cut cardiovascular disease risk among these women, he said, like eating a healthier diet, getting more exercise, not smoking and controlling cholesterol.
But he added, "There are other ways of doing contraception. Oral contraception is not the only possibility."
Dr. Gordon Tomaselli, a Johns Hopkins University cardiologist and American Heart Association official, said he was surprised by the findings.
"It's a bit eye-opening, I think," Tomaselli said in an interview.
He noted that the European women in the study may differ from Americans but said the findings need to be factored into the equation for women deciding whether to take the pill.
"What would I tell my daughter to do? I might suggest maybe not oral contraception," Tomaselli said.
The introduction of "The Pill" in the 1960s revolutionized birth control practices and was a major cultural milestone. The pill uses hormones to suppress ovulation.
Rietzschel said it was possible the findings indicated that there could be an upswing in heart disease among women who have taken the pill, considering that those who began in the 1960s were now reaching a peak age for such illness.
"We might be at the foot of a wave. But the wave might be a small ripple," Rietzschel said.
Many studies have looked at the medical consequences of using the pill. For example, experts say cigarette smoking raises the risk of serious side effects, including heart attacks, blood clots and strokes.
(Editing by Maggie Fox and John O'Callaghan)