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Pill Doesn't Greatly Increase Risk of Blood Clots

WebMD Health News

Aug. 18, 2000 -- Five years ago, doctors and patients became alarmed by reports that some newer combination birth control pills might double or even triple the risk of blood clots in the veins. In the U.S., the FDA made no move to ban or issue warnings about the pills, choosing instead to wait for more information. But in the U.K., the 'pill scare' caused many women to stop taking the pill or change their birth control method.

Now a study in the current issue of British Medical Journal refutes the contention of some of those reports that blood clots are increased by taking the newer forms of birth control pills compared to older forms of the pill. The study tracked the rate of blood clots and found that it stayed virtually the same when looking at the incidence in women in taking the pill in the years immediately before the pill scare and the years immediately after.

"If [the newer pills] had twice the risk of [blood clots in the veins] compared with older formulations, a reduction in their use would be expected to reduce [their] incidence," report Professor R.D.T. Farmer and colleagues from the University of Surrey in England. "We found no such change. No evidence of a difference was seen in any of the age groups."

An estimated 70 million women take some form of birth control pill daily. The pill is said to be the most thoroughly researched of all available medications and the most effective birth control method available. The combination pill contains two hormones, estrogen and progestogen, that work together to prevent pregnancy.

Since the early 1960s, there have been reports of a link between use of the pill and risk of blood clots in the veins. The risk decreased with the introduction of a low-dose pill containing less estrogen, but three reports issued in 1995 suggested that rates were on the rise.

In the latest study, use of the pill decreased from 54% of women surveyed before the pill scare of 1995 to 14% three years later. Farmer and colleagues found that the group of women most likely to stop taking the pill after the scare were those under age 30.

"That's incredibly troubling because obviously what we're looking at is the most fertile group of women, women who have the greatest risk for unintended pregnancy," Lee Shulman, MD, tells WebMD.

"If you decrease the use of reliable, safe contraceptive options, you're going to markedly increase the risk for unplanned and unintended pregnancy and those events, besides having the obvious social and personal ramifications, have a profound medical ramification." In fact, Shulman says, pregnancy actually increases the risk of clots in the veins by six- to eightfold, so any risk of clots from the pill is actually less than it would be if the woman became pregnant.

Shulman says the study serves to confirm that even if there is an increased risk of blood clots associated with use of the pill, it is not as high as many of the reports initially suggested. He says while it will probably be difficult to restore some young women's confidence in the pill, studies like this should help reduce some of the earlier fears. In addition, he says the good news is newer contraceptives are on the horizon.

"Hopefully we will continue to develop newer pills that are going to be more in line with women's lifestyles and allow them to access safe, reliable, and effective contraception," he says.


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