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Many Women Not On Lowest-Risk Birth Control Pills

Posted on: Friday, 14 August 2009, 12:15 CDT

New information has led researchers to believe that many women are not taking the safest brand of birth control pills.

It has been found that certain oral contraceptives have been linked to a higher risk of blood clot than others in two separate studies published by the British Medical Journal.

However, experts emphasize that this is not a common side-effect of the combined pill and that regardless of what brand is used, there is little risk of developing a blood clot. 

The Family Planning Association encourages women to consult their doctors about any concerns they have, rather than just quit taking the pill.

The medical community has long been aware of the connection between the combined pill, which contains both estrogen and progestogen, and an increased risk of blood clots forming in a vein.

In more serious cases, a clot can be fatal, especially if it breaks away and travels to the lungs. 

Over the years, they have reduced the levels of estrogen in the pill in order to lower the risks. However, it is still far more likely for a woman to develop a clot during pregnancy.

Dutch researchers performing the first study examined data from 1,524 women who had developed venous thrombosis (blood clot in the vein). They discovered that, overall, taking the pill was linked with a five-fold increased risk of a clot.

A closer look revealed variation. Women who take pills containing a progestogen called levonorgestrel (for example, Microgynon) had the lowest risk of thrombosis at four times that of women not on the pill.

On the other hand, those taking contraceptives containing desogestrel (for example, Mercilon or Marvelon) had the highest risk, at seven times that of those not taking the pill.

For women taking a pill with norgestimate (for example, Cilest) there was an almost six-fold extra risk as did those on drospirenone (for example, Yasmin).

Those taking a drug containing cyproterone acetate (for example, Dianette, which is often prescribed for acne) had an almost seven-fold additional risk.

The researchers concluded, "Currently available oral contraceptives still have a major impact on thrombosis occurrence and many women do not use the safest brands with regard to risk of venous thrombosis." 

The second study was conducted by Danish researchers who also found that contraceptives containing levonorgestrel were connected with a lower risk than those containing desogestrel, gestodene or drospirenone.

GP and senior lecturer at the University of Southampton Dr. Nick Dunn found it to be a point of interest that the newest type of pill Yasmine did not actually have any advantage over the more traditional pills.

However, he did add that the pills recommended by the researchers were probably already the ones most commonly prescribed.

"What this says is we should stick to prescribing the well-trusted favorites but the chance of having a blood clot when on the pill are very low anyway," he said.

If a woman were to prefer a certain brand name because of a personal experience, he said he would still prescribe it.

Lynn Hearton, of the Family Planning Association (FPA), said, "Although the combined pill does slightly increase the risk of thrombosis, the risk is still really low.”

She added, "If any women are worried about the pill they should not stop using it…they should continue taking it and seek advice from a health professional."

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On the Net:

• British Medical Journal

Source: redOrbit Staff & Wire Reports

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