MONTREAL, Aug. 29 (UPI) -- Women who take third-generation birth control pills containing desogestrel or gestodene show no increased risk for heart attack compared to women who take no birth control pills, a new study reports.
The third-generation pills also seem to cut heart attack risk in half vs. second-generation pills containing norgestrel or levonorgestrel, according to the study.
"Recent controversies about OCs (oral contraceptives), in particular third-generation OCs, have dwelt upon blood clots in the veins," said lead investigator Walter Spitzer of McGill University. "Less attention has been paid to the safety record of newer OCs in respect to the arteries."
Blood clot blockages of arteries in the heart are a cause of heart attacks.
Spitzer, who is emeritus professor of epidemiology, the study of disease in populations, and colleagues looked through all the published literature in French and English containing studies on birth control pills and heart attacks and found 29 studies. They used a method of taking subjects from many studies and combining the results to achieve a type of statistical power that individual studies taken alone cannot provide, due to the relatively small numbers in each study. This kind of approach is called a meta-analysis.
The researchers found, among women who do not take birth control pills, about one in 100,000 will have a heart attack in a given year, about the same rate the study found for those taking the third-generation pills. The first-generation pills caused women to have about nine times as many heart attacks as women not on the pill, they found.
The first birth control pills marketed contained very high doses of estrogen, a hormone that suppresses ovulation.
In the second-generation pills, estrogen levels were lowered significantly and norgestrel or levonorgestrel -- each a form of hormone called progestins -- was added. Progestins inhibit ovulation by suppressing a hormone in the pituitary gland and also cause mucus to thicken on the cervix, forming a barrier to fertilization of the egg by the sperm.
The third-generation pills changed the type of progestin to desogestrel or gestodene so that cholesterol-raising effects and tendency to promote weight gain were reduced.
There have been questions about second- and third-generation pills and strokes caused from blood clots in the veins. A study of 203 women with strokes done at University Medical Center in Utrecht, the Netherlands, and released earlier this year reported women taking second- and third-generation pills show increased stroke rates. Women taking no pills showed a rate equivalent to 30 strokes per 100,000 compared to about 60 strokes per 100,000 for women taking second- or third-generation pills, still somewhat less than the risk of stroke during pregnancy.
Spitzer told United Press International he thinks the Utrecht stroke study lacked sufficient statistical power to be conclusive.
"In general, (the study) doesn't look like there's an increased risk ... (The finding) may be true for young healthy women who are pre-plaque-deposition and have whistle-clean coronaries, but those are probably not the ones who are going to have (a heart attack), anyway," Andrea Rapkin, professor of obstetrics and gynecology at the David Geffen School of Medicine at the University of California at Los Angeles, told UPI.
Roger Blumenthal, director of preventive cardiology at Johns Hopkins Hospital in Baltimore, told UPI, "The study doesn't see any association with cardiac events, with these types of what are called third generation oral contraceptives. They say that this means that you wouldn't deny women birth control pills if you're concerned about a heart attack because the data doesn't really support it."
Blumenthal pointed out, however, that some high-risk women, such as smokers or some with elevated blood pressure, would not be placed on birth control pills, regardless of this study's findings.
The research appears in the Aug. 30 issue of the journal Human Reproduction.
(Reported by Joe Grossman, UPI Science News, in Santa Cruz, Calif.)
