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A study published in the BMJ looks at hormonal contraceptives and the risk of heart attacks and strokes.
Dr Sonya Babu-Narayan, Clinical Director at the British Heart Foundation and consultant cardiologist, said:
“You shouldn’t be overly alarmed by these findings if you are using or considering starting hormonal contraception. The additional risk of heart attack and stroke is very low for the vast majority – it’s equivalent to one extra heart attack for every 10,000 women using hormonal contraception for a year. And pregnancy itself also increases your risk of developing blood clots, stroke and heart attack.
“When considering hormonal contraception options, you will be able to discuss the risks and benefits with your GP so that you can make an informed decision about what is best for you. This could include discussion and management of your existing cardiovascular risk factors like high blood pressure, diabetes, smoking, or if you are living with obesity.
“The study lends weight to previous evidence of an association between hormonal contraception use and a small increase in the number of heart attacks and strokes. The researchers made use of a wealth of long-term electronic healthcare information from over 2 million people in Denmark – this scale and breadth makes the findings more reliable and complete than previous studies and enables study of even rare complications like these.
“However, the study is observational so it can’t prove cause and effect, and there may be other factors at play driving the links seen that aren’t sufficiently accounted for.
“This latest study supports the current practice of recommending the option of a progestin intrauterine device – the hormonal coil – for those already living with high cardiovascular risk, as this wasn’t linked to more heart attacks and strokes.”
Dr Becky Mawson, NIHR Clinical Lecturer in Primary Care, and GP with special interest in sexual and reproductive health, University of Sheffield, said:
“Please do not stop using contraception based on this study! The risk of stroke and heart attack in pregnancy and postnatal period is significantly higher than the risks reported in this study for contraceptives. For those using contraceptives for treatment of health conditions, the slightly increased risk needs to be balanced with the benefit in quality of life for those suffering debilitating gynaecological and hormonal conditions.
“Saying that, if you have other risk factors for strokes and heart disease, then it is worth discussing with your healthcare team to look at the safest options like the hormonal coil. This observational study looks at relationships in data, not causes. It adds to previous studies within the same database looking at increased blood clot risk.
“While it remains true as it has done for years that we need to find better, risk-free alternatives to prevent pregnancy, in my view this study hasn’t changed that and should not cause alarm but does add to growing knowledge in this area.”
Dr Clare Arnott, Conjoint Associate Professor, Cardiologist and Head of Cardiovascular Program, The George Institute for Global Health, and UNSW Sydney, said:
“This is an interesting, timely and important study. It is wonderful to see sex-specific cardiovascular risk factors given appropriate attention in medical research.
“The study identified twice the risk of stroke and heart attack in those exposed to the combined oral contraceptive pill (and around 1.5x the risk for progestin only formulations). Interestingly, while risk was also increased for the combined vaginal ring and patch (with relative risks higher with these preparations), no increased risk was observed for the progestin-only IUD. Also of note, and clinical relevance, duration of use did not appear to impact risk.
“While these relative risks are important, particularly at a public health/population level, it should be noted that absolute risk remains low in this patient population of young women. It is also important to note that this study excluded women with a history of arterial thrombosis – a high risk group, and thus these results cannot be extrapolated to that population.
“The study is strengthened by a large cohort size, which is nationally representative, long patient follow up period, and is adequately powered with respect to the number of events recorded. Of course, as the authors rightly acknowledge, this is observational research, and correlation is not the same as causation.
“Nonetheless, it is valuable information that should be routinely communicated to women to allow them, in conjunction with their healthcare provider, to make informed decisions about their health. These data are also very important at a public health/ population level given the >200 million women worldwide using hormonal contraception, and thus public health clinicians and policy makers should take note.”
Prof Angela Clerk, Professor of Biomedical Science, University of Reading, said:
“The study appears to be comprehensive and rigorous, representing the whole of the Danish population. There should be some caution in extrapolating to other populations with different ethnicities, since genetic background and cultural variation could affect cardiovascular risk, and some ethnicities not fully covered by the Danish population could have greater vulnerability.
“This is clearly an important study but, while the focus is on the potential negative effects of contraception on cardiovascular risk, it is also clear that any increase in risk is actually very small. This emphasises the overall safety of the drugs, particularly when balanced against the negative effects of unwanted pregnancies resulting from a lack of contraception. Yes, there should be informed choice of the type of contraception, but perhaps lifestyle choices need to take greater precedence. Though I am past that stage, this study would not stop me from using any of these forms of contraception over not using one and facing an unplanned pregnancy.”
Dr Channa Jayasena, Reader in Reproductive Endocrinology at Imperial College London, and Consultant in Reproductive Endocrinology and Andrology at Imperial College Healthcare NHS Trust, said:
“Contraceptive medication is a vital healthcare option, which offers lower chances of accidental pregnancy compared with barrier contraceptive methods. Contraceptives work by using high doses of female hormones like oestrogen and / or progesterone to temporarily ‘switch off’ the ovaries and womb. Oestrogen is a ‘sticky’ hormone because it makes blood more likely to clot. It is well-known that The Pill increases blood clot risk. Increased blood clot risk increases risks of related problems like stroke and heart attack. The current study helps to define the risks of different types of contraceptive medication.
“The study is well designed because looks at health records from 2 million women of reproductive age living in Denmark. The authors were careful to adjust for factors which might have affected the results. The findings confirm that The Pill is associated with increased risks of stroke and heart attack. Observational studies like this one cannot conclude that the Pill has caused stroke and heart attack; but our prior knowledge of how the pill works makes this likely.
“My biggest criticism is the way that the results are presented. Only 3 per 1000 women were affected by a stroke or heart attack; the risk among those on the pill was about 6-10 per 1000. The absolute risk of having a stroke or heart attack on The Pill is still very low.
“Women should take away the importance of smoking cessation, healthy eating, and exercise to minimise the (small) increased risk of stroke or heart attack associated with being on the pill. Women who have high risks of stroke or heart attack that cannot be reduced should strongly consider a hormonal coil, because of its lack of associated increased stroke or heart attack risk.”
‘Stroke and myocardial infarction with contemporary hormonal contraception: real-world, nationwide, prospective cohort study’ by Harman Yonis et al. was published in the BMJ at 23:30 UK time on Wednesday 12 February 2025.
DOI: 10.1136/bmj-2024-082801
Declared interests
Dr Sonya Babu-Narayan: “No conflicts of interests to declare.”
Dr Becky Mawson: “Current project with South Yorkshire Digital Health Hub – The Hormone Effect – developing an app to collect data on side effects of contraception.
Research lead (unpaid and no financial benefits) – The Lowdown Women’s Health Platform.”
Dr Clare Arnott: “None to declare.”
Prof Angela Clerk: “I no conflict of interest under any of the categories below with respect to industry funding. I have no conflict of interest with any of my own research under these categories either. I am a woman, however.”
Dr Channa Jayasena: “No conflicts to declare.”