All but one common contraceptives linked to increased stroke and heart attack risk, study finds
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Some hormonal contraceptives are linked with a higher risk of heart attack and stroke, according to new research which also found one form of contraceptive has no increased risk of those serious cardiovascular events.
Experts said the risks were still very low, but it was important for women to be fully informed when considering their contraceptive choices.
The researchers tracked the prescription records of more than two million Danish women aged 15 to 49 between 1996 and 2021, to see whether modern contraceptives increased the risk of ischemic stroke and heart attack compared to women who did not use hormonal contraceptives.
The research, published in BMJ on Wednesday, found there was a greater risk of both heart attack and stroke linked to most forms of hormonal contraceptives.
The greatest risk came from oestrogen-containing products, particularly the vaginal ring and skin patch. The vaginal ring increased the risk of heart attack 3.8 fold, while the patch increased ischaemic stroke risk 3.4 fold.
The combined oestrogen-progesterone pill was associated with twice the risk of ischaemic stroke and heart attack. The increased risk translated to one extra stroke for every 4,760 using the combined pill for one year, and one extra heart attack for every 10,000 women for each year of use.
Progestin-only contraceptives including pills and implants also had a slightly higher risk of heart attack and stroke, although the risk was lower than the combined pill.
The study found the progestin-only intrauterine device (or IUD) was the only hormonal contraceptive not linked to an increased risk of either a heart attack or stroke.
The researchers concluded: “Although absolute risks were low, clinicians should include the potential risk of arterial thrombosis in their assessment of the benefits and risks when prescribing hormonal contraceptive method.”
In the UK, the use of oral contraceptives has continued to decline while the use of long-acting reversible contraceptives including the hormonal IUD has risen in recent years.
In 2022/23, 36.2 per cent of those under 25 chose a long-acting method compared to 27.6 per cent in 2018/19, according to government data. In over 25s, it has risen from 43.8 per cent in 2018/19 to 53.2 per cent in 2022/23.
An estimated nearly 248 million women around the world use hormonal contraceptives, and postdoctoral researcher Therese Johansson said it was important for women to understand the potential risks, however small, of their hormonal contraceptives.
“It is important to note that the absolute risk remains low. Nonetheless, these side effects are serious and given that approximately 248 million women use hormonal contraceptives daily, the results carry important implications,” she wrote in an accompanying opinion piece published in BMJ.
“Contraceptive counselling requires a careful assessment of individual risk factors, such as pre-existing cardiovascular risk factors, including hypertension, obesity, or smoking.”
Dr Johansson said the study showed that the levonorgestrel-releasing intrauterine system, which is more commonly known by the brand name Mirena, was the safest option.
“The levonorgestrel-releasing intrauterine system was the only hormonal contraceptive not linked to an increased risk, making this option safer for cardiovascular health,” she said.
“Policy makers should prioritise making safer alternatives, such as the levonorgestrel releasing intrauterine system for women with cardiovascular risk factors, both affordable and accessible, particularly in low resource settings where cardiovascular risks are frequently underdiagnosed and untreated.”
Dr Becky Mawson, NIHR Clinical Lecturer in Primary Care, and GP with special interest in sexual and reproductive health, University of Sheffield, said women should not be alarmed by the study’s results.
“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,” she said.
“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.
“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.”
