Women who take the combined contraceptive pill containing one of the newer progestogen hormone formulations have twice the risk of dangerous blood clots, which can lead to DVT (deep venous thrombosis) and pulmonary embolism, than those on the older formulations of pill.

This is the main finding from a study published by the British Medical Journal that highlights the difference in risk between older and newer types of contraceptive pills.

The results show that women on the older pill formulations, containing levonorgestrel, norethisterone and norgestimate, have an increased risk of clots about two and a half times that of women not on the pill.

But those using newer drug preparations, containing drospirenone, desogestrel, gestodene and cyproterone, have an even higher increased risk of dangerous blood clots of around 4 times those not on the pill.

However, the authors are not suggesting the pill is unsafe, pointing out that pregnant women have up to a 10-fold increase risk of blood clots.

The number of extra cases of blood clots per year per 10,000 treated women is lowest for levonorgestrel and norgestimate, and highest for desogestrel and cyproterone.

While the study is UK based, it is relevant to Australia where oral contraceptive use is around 33%; significantly higher than other developed countries, which average 18%.

Last Reviewed: 28/05/2015