A new study has linked most hormonal contraceptives to a higher risk of heart attacks and strokes.
The paper, published in the British Medical Journal, looked at the prescription records of more than two million healthy Danish women (meaning they had no history of conditions including thrombosis, cancer, and gynaecological diseases, among others) aged 15 to 49 between 1996 and 2021.
Among those who had used hormonal contraceptives, including the pill, the implant and coils, there were 21 extra ischaemic strokes and 10 extra heart attacks per 100,000 people a year. However, some contraceptives had a higher risk factor while others showed no risk.
What does this study show about link between hormonal contraceptives and heart attack and stroke risk?
'This extensive research offers important information about cardiovascular health and the impact of hormonal contraception,' says Dr Melanie Davis-Hall, medical director at The Lowdown, a contraceptive review site.
'The study indicates that certain hormonal contraceptives are associated with a slight increase in the risk of ischaemic stroke (caused by a blood clot in the arteries supplying the brain) and heart attack (caused by a blood clot in the arteries supplying the muscle of the heart).
'Existing studies suggested an increased risk of these events with hormonal contraception use, but findings have been inconsistent and from outdated studies and evidence on the effects of mode of administration, oestrogen type, progestogen type and duration of use was lacking.
This study shows that combined contraceptives (containing both oestrogen and progestogen), such as the pill, were linked to a twofold increase in these risks. Non-oral combined methods, like the vaginal ring and patch, were associated with even higher relative risks. For instance, the vaginal ring was linked to a 2.4-fold increase in stroke risk and a 3.8-fold increase in heart attack risk.
In contrast, progestogen-only contraceptives – including the progestogen-only pill (mini pill), contraceptive injection, implant and hormonal coil (also known as the intrauterine system (IUS) or hormonal intrauterine device (IUD)) showed little to no increased risk, although this was based on limited data. The hormonal IUD (coil) in particular was not associated with an increased risk.'
Dr Oliver Segal, a consultant cardiologist and electrophysiologist at The Harley Street Clinic, part of HCA Healthcare UK, explains that this may happen because, 'Oestrogen increases the production of clotting factors while reducing natural anticoagulants (which stop blood clotting), shifting the balance towards a greater risk of thrombosis.
'Contraceptives also can raise blood pressure by promoting fluid retention and affecting vascular tone.'
Both Dr Hall and Dr Segal are keen to say that, while the risk is higher for women on contraception, the study shows it is still very low.
'This is because the baseline risks of ischaemic stroke and heart attack among women of reproductive age is already very low. For example, using the combined pill translates to one additional ischaemic stroke per 4,760 women per year and one additional heart attack per 10,000 women per year,' says Dr Hall.
How worried should women using contraception be about heart attacks and stroke?
'Women should not be alarmed,' says Hall. However, she would encourage everyone to talk with a doctor or healthcare provider to make the best choice for them.
There are also some women who may want to take extra note of this study. 'Women with existing cardiovascular risk factors – such as high blood pressure, obesity, smoking, a history of blood clots, migraines with aura or a family history of stroke or heart disease – may face a higher absolute risk when using combined hormonal contraceptives. For these individuals, non-oestrogen-containing methods or non-hormonal methods may be considered more suitable,' explains Hall.
Dr Segal adds: 'Smokers over 35 should not take combined oestrogen-progestogen contraceptives, as the clotting risk is significantly higher.'
The most important thing is that you don't abruptly stop using your medication. 'The small increased risk of stroke or heart attack must be weighed against the benefits of hormonal contraception, including pregnancy prevention, menstrual cycle regulation and treatment of conditions such as polycystic ovary syndrome (PCOS) or endometriosis,' says Dr Segal.
Dr Hall says: 'Moreover, pregnancy and the postpartum period inherently carry higher risks of cardiovascular events than those associated with the use of hormonal contraceptives.' Meaning: if you're worried about your heart health or stroke risk, coming off contraception and getting pregnant may be riskier.'
The pill and health risks: what's going on?
This likely won't be the first study you've seen linking hormonal contraception to a higher risk of health events. It's been linked with higher rates of cervical cancer, breast cancer and depression, among other adverse affects.
Alice Pelton, The Lowdown's founder and CEO, says these findings may actually be a good thing. 'Good in that people are still investing time and money into research into contraceptive methods that have been around for decades. But the bad side is that we’re still understanding how these drugs impact us,' she says.
Around 26% of women aged 16 to 49 in the United Kingdom report using hormonal contraception, according to another study from the BMJ. 'It’s not fair that the burden is on women, and at The Lowdown we have consistently called for better investment into new methods to prevent pregnancy, that are for men and women,' adds Pelton.
Worldwide, there are 248 million hormonal contraceptive users, which, according to Dr Segal, means 'even a small increase in risk translates into thousands of additional cases of stroke and heart attack each year. This makes it crucial to continue researching ways to make contraception safer.
'Newer formulations in contraceptives are designed to reduce the risks by using lower levels of oestrogen, however long-term studies are needed to fully understand their safety profile. And we still need better alternatives: ideally, future contraceptive methods should provide effective birth control without increasing cardiovascular risk, and research is ongoing to develop non-hormonal options that do not interfere with clotting mechanisms.'
What's the best contraception?
The best contraception for you is one that works with your body, health and lifestyle. Always talk to your doctor about the types of hormonal contraception that might have a negative side effect for you and remember what works for one person won't work for another.
Once you know what to look for or what to avoid, you can you can read other people's reviews of hormonal contraception at The Lowdown.
While there are plenty of reasons to take hormonal contraception, there are others methods can try. 'The only long acting non hormonal contraceptive on the market is the copper coil (IUD) which is a small, T-shaped device made of plastic and copper that is inserted into your womb by a doctor or nurse.
'It is a very popular non-hormonal method for The Lowdown community as it's very effective and lasts over five years. Like all methods, it comes with risks like a small increase of infection or perforation of the uterus,' explains Pelton.
More like this:
New data shows a 14% rise in women using no contraception at all
'After three years off hormonal contraception, here's what I learned'
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