Combined Oral Contraceptives: Old Scare, New Data

I vaguely remember the pill scare of 1995; acres of media coverage, scary headlines and confused messages – I recall thousands of women stopping their contraception overnight for fear of a clot forming by morning, and scores of unplanned pregnancies as a result – but then maybe the way the statistics from the fallout were reported was as unreliable as the reporting of the science behind the original story. I was working as a junior doctor on a medical ward at the time; I didn’t need to think that much about contraception which might account for why my memory is hazy.

There was another pill scare this weekend, and I’m glad to say that there wasn’t too much media hysteria this time, but the story is still important and it will have caused many women to double-check their pill against the list in the newspaper – some will have been relieved to find their chosen brand to be in the clear, and other will be wondering what it means for them. The Mail, of course, couldn’t resist using the word Deadly’ in its headline, and relished the idea of ‘Every GP in Britain’ being told to do something, but the print of the article was reasonably measured, perhaps reflecting the fact that this is not a new story; far from it, there was no new research here, just an updated review of what we learned back in 1995 and some slightly adjusted figures.

It’s not bad to be reminded, though, that the contraceptive pill, like every other medicine we ever prescribe, is not entirely risk-free, and that both the risks and benefits of the pill do vary slightly with the brand. The review, by the European Medicines Agency, looked at the risk of blood clots, both in veins (Deep Vein Thrombosis or DVT and Pulmonary Embolism or PE) and arteries (stroke), which are two of the biggest safety concerns associated with the combined pill.

The first thing to say is that the risk of a clot is only increased with combined pills that contain oestrogen and progesterone (usually taken for 21 days followed by a 7 day gap), and that there is no risk of clots associated with the mini-pill, which contains progesterone only (eg Micronor, Cerazette or Cerelle) and are usually taken daily without a break.

We have known for a long time that the combined pills increased the risk of DVT, but what was new information in 1995, and caused the scare, was that the risk was different with different pills. At that time evidence emerged that older pills, like Microgynon, were safer than the newer pills, like Marvelon. Most women found that the older versions suited them just fine, but some women felt better on the newer pills – perhaps their skin was in better condition, or they had less PMT – and so these had become quite popular. What ensued nearly 20 years ago was a rather panicked move away from these pills, before the pendulum reset itself as people realised that the increased risk was not that great, and having good skin or not turning into a growling  bear on a monthly basis was actually quite important.

More recently there have been newer pills still – Yasmin being the most notable example – that promised to suit women even better than the older ‘new’ pills. There is no doubt that doctors and patients have been swayed a little by the idea that these pills are somehow ‘more feminine’, when actually most women feel no inhibition to their sense of womanhood on the tried and tested varieties, and the newest pills also seem to carry the slightly higher risk of DVT.

So what are the risks? Well the important thing here is to pay most attention to the absolute risk linked with each pill, and for each woman to ask if that is a risk she is prepared to take in order to find a reliable contraception that suits her. The headlines often quote the relative risk – ‘They are believed to double the risk compared to older varieties’  is more eye-catching than ‘About 1 in a 1000 women will develop a DVT’. While comparing the risk between different pills is important in deciding which pill to try, once you have decided which pill to use the fact that there might be a less risky pill out there becomes an irrelevance – what matters is whether you are comfortable with the level of risk attached to the pill you are taking.

The EMA review, therefore, is a useful reminder that no woman should start the combined pill without a discussion with her doctor about the risk of DVT, and that we should always start with the lowest risk pill unless there is a very good reason not to. It is also instructive to look at the estimates of risk given in this new review, as they are higher across the board (even for women who are not on the pill) than the estimates currently provided in the British National Formulary that most GPs in the UK will be using. I have tabulated the figures below for comparison – and I shall now be converting to the EMA figures, since I would always rather over-estimate a risk like this than under-estimate it.

 

The worst risk, therefore, is 120 per 100,000 – which is not insignificant, although it is worth remembering that this still means that 99,880 women out of every 100,000 on the highest risk pills will not get a DVT. The risk will also be lower if you have no risk factors – such as a family history of DVT/PE, smoking or being significantly overweight. When a DVT does occur it is usually in the first year – which supports the fact that if you are already well established on one of these pills there is no need to panic, and certainly no reason to stop the pill without first speaking to your doctor.

A final note about arterial clots (stroke); this was also reviewed in the EMA report, and although they did not report on the absolute risk other than it being low, it was reassuring that there was no difference in the rate of arterial problems between the different pills.

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