Pill clotting risk could be reduced - experts

Friday August 14th, 2009

Women taking the contraceptive pill still face a risk of dangerous blood clots - and do not always get the safest brands, experts warned today.

Overall women taking the "pill" face a five times increased risk of developing clots in the veins - venous thrombosis, according to a new analysis published by the British Medical Journal.

Dr Astrid van Hylckama Vlieg, of Leiden University, the Netherlands, and colleagues gathered information on 1,524 women under the age of 50 with deep venous thrombosis, and 1,760 similar healthy women.

Women who were taking oral contraceptives had a risk of venous thrombosis five times higher than women who were not. But the risk "clearly differed by type of progestogen and dose of oestrogen", say the researchers.

They found that pills containing levonorgestrel or norethisterone, plus a low dose of oestrogen, carried the lowest risk.

"Currently available oral contraceptives still have a major impact on thrombosis occurrence," they conclude.

Also in the journal, researchers led by Professor Ojvind Lidegaard at Rigshospitalet, Denmark, report on a similar study using a national database. Among the population studied, there were 4,213 cases of venous thrombosis.

The overall risk was 6.29 per 10,000 users of oral contraceptives and 3.01 per 10,000 non-users. The risk declined after the first few months of use.

Again, pills containing levonorgestrel and lower dose of oestrogen were found to be the safest. "Progestogen only pills were not associated with any increased risk of venous thrombosis," they add.

In an editorial, Dr Nick Dunn of Southampton University, UK, states that the risk is still low, at 15-25 per 100,000 person-years, compared with five for non-users.

"Contrary to popular belief, obesity (despite being associated with venous thromboembolism) is not a contraindication to using the pill, although choosing low risk varieties is sensible," he adds.

Hylckama Vlieg, A. The venous thrombotic risk of oral contraceptives, effects of oestrogen dose and progestogen type: results of the MEGA case-control study. The British Medical Journal, 2009;339:b2921.

Lidegaard, O. et al. Hormonal contraception and risk of venous thromboembolism: national follow-up study. The British Medical Journal, 2009;339:b2890.

Dunn, N. Oral contraceptives and venous thromboembolism. The British Medical Journal, 2009;339:b3164.

Tags: Europe | Heart Health | Pharmaceuticals | UK News | Women’s Health & Gynaecology

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