Blood clots on the contraceptive pill are rare

Two studies in the British Medical Journal found that oral contraceptives were linked with a far higher risk of blood clot than others.

But experts stressed that blood clots are a rare side-effect, and the risk is small whichever brand is taken.

It has been known for a long time that the combined bill – containing both oestrogen and progestogen, was associated with an increased risk of a type of blood clot that forms in a vein. In some cases a clot can be serious and occasionally fatal, particularly if the clot breaks away and travels to the lungs.

In a study of 1,524 women who had developed the blood clot it was found that overall taking the pill meant they were five times as likely to get a clot. Closer analysis showed women taking pills containing a progestogen called levonorgestrel for example Microgynon, had the lowest risk at four times that of women not on the pill.

Whereas those on contraceptives containing desogestrel for example, Mercilon or Marvelon had the highest risk, at seven times that of those not taking the pill.
Women taking a pill with norgestimate for example, Cilest had an almost six-fold added 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.

Lynn Hearton from the Family Planning Association (FPA) says, ‘Although the combined pill does slightly increase the risk of thrombosis the risk is still really low. 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.’