SAN ANTONIO, Feb. 7 (UPI) -- The new low-dose birth control pills, so-called estrogen-lite pills, are no safer than earlier formulations of the contraceptives, stroke researchers reported Thursday at the 27th International Stroke Conference.
Earlier research linked birth control pills to increased risk for ischemic stroke, the type of stroke caused by blood clots that cut off the flow of blood to the brain.
"We found that any use of any oral contraceptive increases the risk of ischemic stroke by about two-fold," Dr. Ale Algra, associate professor of clinical epidemiology at University Medical Center, Utrecht, Netherlands, told United Press International. "In absolute terms, this means that the number of women having ischemic strokes from taking any oral contraceptive increases from three women per 10,000 to six per 10,000 a year," Algra said.
Producers of oral contraceptives mix synthetic female hormones. Early birth control pills developed and approved in the 1960s contain high levels of estrogens and of the progestogens lynestrenol or norethisterone. Subsequent research indicated these hormonal combinations increase the risk of blood clot development. Blood clots can go to the heart, causing a heart attack, or to the brain, causing a stroke.
Second-generation oral contraceptives, developed and approved in the 1970s, contained less than 50 micrograms of estrogen and an alternative progestogen, levonorgestrel. These pills were developed to reduce the side effect of blood clotting.
Third-generation oral contraceptives, developed and approved in the 1980s, lowered side effects associated with the progestogens in the second-generation pills -- weight gain, acne and increase in cholesterol levels. Third-generation pills also used less estrogen than the first generation and combined it with other progestogens, desogestrel or gestodene.
The Dutch researchers evaluated the risk of ischemic stroke for all three generations of oral contraceptives. They found the risk of stroke in women taking any type of oral contraceptive to be 2.3 times that of women not taking one.
Women using the first-generation pill were 1.7 times more likely to have a stroke than women not using any oral birth control. Women taking the third-generation pill increased their stroke risk 2.2 times compared to those not taking any oral contraceptive. Those taking the second-generation pill formulations had 2.4 times the risk, Algra said.
Smoking, hypertension, diabetes and high cholesterol raised stroke risk in all pill users in the Dutch study.
Algra and his team had previously tied third-generation oral contraceptives to increased risk of blood clot formation in the deep veins of the legs, called venous thrombosis. They also found a higher risk of venous thrombosis in third generation pill users than in second-generation pill users. Venous thrombosis clots can move to the lungs, causing a potentially fatal pulmonary embolism.
"Because there is virtually no difference in the risk of stroke in second- and third-generation pills, the balance of the decision whether to use second- or third-generation oral contraceptives should be determined by the risk of venous thrombosis, blood clots deep in the leg," Algra said. "They seriously should consider using second-generation preparations if they did not use OCs before, or switching from third-generation pills to second-generation pills if they are current users," he added.
Dr. Fenwick Nichols, a professor of neurology at Medical College of Georgia at Augusta, urged the findings be interpreted very cautiously.
He noted, for example, the reported increased risk is "still a very small risk." For most women, "the medical risks of pregnancy are greater than the risks of birth control pills," he told UPI.
