Study Finds Certain Kinds of Birth Control Could Raise Stroke, Heart Attack Risk But experts say the finding is complicated
A recent study linked some hormonal birth controls to a higher risk of stroke and heart attack
Cris Cantón / Getty Images
- A recent study linked some hormonal birth controls to higher stroke and heart attack risk.
- Vaginal rings, skin patches, and the pill containing both estrogen and progestin had the highest risk.
- Cardiovascular risk from birth control is low overall, but experts recommend talking to a healthcare provider to pick the safest option for you.
Several forms of hormonal birth control could come with a higher risk for ischemic stroke and heart attack, recent research found.
The study, published in The BMJ on Feb. 12, investigated contraceptive use and cardiovascular risk in over 2 million Danish women.
As compared to those who didn’t use hormonal contraception, women had the greatest risk if they used a combined vaginal ring or a combined skin patch (meaning the contraceptive contained both estrogen and progestin). The ring raised women’s stroke risk 2.4-fold and heart attack risk 3.8-fold, while the patch increased stroke risk 3.4-fold.
The combined pill—which also contains both estrogen and progestin, and is the most commonly used form of birth control—came with double the risk of stroke and heart attack, the data showed.
Progestin-only contraceptives, including pills and implants, also led to slightly higher stroke and heart attack risks, though they were lower than combined pills.
Despite these findings, the researchers emphasized that the risks of using these contraceptives are still pretty low.
“Although hormonal contraception was found to increase cardiovascular risk, the number of women expected to have a heart attack or stroke due to hormonal contraception is still really quite small,” said Jennifer Lewey, MD, MPH, director of the Penn Medicine Women’s Cardiovascular Health Program and assistant professor of cardiovascular medicine at the University of Pennsylvania Perelman School of Medicine.
Evaluating Contraception and Cardiovascular Risk
This study relies on data collected between 1996 and 2021 from over 2 million Danish women, all of whom were between the ages of 15 and 49. At the start of the study, none of the participants had a history of blood clots, endometriosis, or polycystic ovarian syndrome, among other health conditions.
During that time, researchers recorded 4,730 strokes and 2,072 heart attacks among the participants. They also followed participants’ contraception use.
For people who did not use any hormonal birth control, the rate of ischemic stroke was 18 per 100,000 person-years. This means that if you watched 100,000 people not on birth control for a year, there would likely be 18 strokes.
Comparatively, the rate was 39 strokes per 100,000 person-years for women on combined oral birth control pills, 33 for those on progestin-only pills, and 23 for women using levonorgestrel-releasing intrauterine devices (IUDs).
For heart attacks, the incidence rate was 8 per 100,000 person-years for women not using hormonal birth control. It was 18 heart attacks per 100,000 person-years for combined oral contraception users, 13 for progestin-only pill users, and 11 for IUD users.
The researchers also found that use of a combined vaginal ring, patch, and (to a lesser degree) progestin-only implant were associated with increased blood clot risk.
Essentially, the data showed that combined pills, rings, and patches, plus progestin pills and implants, were all linked to varying degrees of elevated risk for stroke, and some for heart attacks.
The one hormonal birth control method that carried no significant risk? IUDs, the study found.
“The levonorgestrel-releasing intrauterine system was the only hormonal contraceptive not linked to an increased risk, making this option safer for cardiovascular health,” Therese Johansson, PhD, a researcher at the Royal Institute of Technology in Sweden, wrote in a related editorial.
Not Quite an Apples-to-Apples Comparison
Though the results of the new study are interesting, there are some limitations.
Importantly, the study doesn’t share any details on the demographics of women who had these adverse health events, Mary Jane Minkin, MD, a gynecologist and clinical professor of obstetrics, gynecology, and reproductive sciences at the Yale School of Medicine, told Health.
Women in Northern Europe have a higher incidence of genes that increase blood clot risk, and “we don’t know the prevalence of these mutations in these women,” Minkin explained. This means it’s not clear if the results would hold up in an American population.
Also, because of the way the study was designed, we don’t know if contraceptives are actually behind this higher incidence of heart attacks and strokes. It’s possible that the women who were prescribed these specific forms of birth control had a higher incidence of underlying conditions, for example.
“Perhaps some of the providers assumed that a patch or vaginal ring might be safer in some higher-risk women, because of obesity or age,” Minkin said.
Why Does Contraception Affect Cardiovascular Health?
This new study is not the first to find a link between hormonal birth control and cardiovascular risks.
A 2012 analysis found a correlation between combined contraceptive pills and stroke and heart attack. Plus, the authors noted, previous research has found an increased risk for blood clots with the patch and the ring, as compared to combined birth control pills.
The hormones in these contraceptives could explain why.
“Estrogen is well known to be prothrombotic [clot-causing],” C. Noel Bairey Merz, MD, professor of cardiology and director of the Barbra Streisand Women’s Heart Center at Cedars Sinai Medical Center, told Health.
And progestogens (a certain class of hormones which include progestins) are known to promote the constriction or narrowing of blood vessels, Merz added.
However, research is mixed. Other studies have shown that progesterone, the naturally occurring version of progestin, can actually relax blood vessels and protect the cardiovascular system.
“Hormones that are ... naturally occurring in the body can improve blood flow and vascular health,” Lewey told Health. But “hormones, when taken in the form of contraception or hormone replacement therapy, may lead to greater risk of forming blood clots.”
Other factors, including genetics, age, and other underlying conditions, can also contribute to how hormonal birth control impacts vascular health, she said.
Choosing a Birth Control That’s Right for You
It’s estimated that nearly 65% of American women and girls ages 15 to 49 use birth control. Given that some carry slightly higher cardiovascular health risks, it’s important to talk to a healthcare provider to make sure you're using the safest option for you.
In general, birth control tends to be safe for most healthy people. In fact, a large 2023 study found that women who took oral contraceptives had a lower risk of all‐cause death, cardiovascular disease events, coronary heart disease, heart failure, and atrial fibrillation.
But women who are older, smoke, or have obesity are at an elevated risk for blood clotting, said Minkin, so combined hormonal birth control may not be the best choice for them. In general, these combined hormonal contraceptives aren’t recommended if you have high blood pressure or if you’re over age 35.
And as the study noted, the specific type of hormonal contraception you take can also make a difference.
The patch and the ring may be riskier because they “continuously release low levels of estrogen,” Lewey said, which “leads to a higher concentration of estrogen in the bloodstream compared to pills.” Again, estrogen is known to raise blood pressure and the risk of clots, Merz said.
Of course, there are other options beyond combined or estrogen-based hormonal contraceptives.
Progestin-only options can be safer if you have an existing cardiovascular condition, as are IUDs, according to the American Heart Association. Plus, condoms, spermicides, and diaphragms won’t impact cardiovascular risk.
“The safest forms of birth control for women with existing cardiovascular disease include non-hormonal contraception, such as copper-IUD and sterilization,” said Lewey.
However, these non-hormonal options do tend to be less effective and put a woman at a higher risk of pregnancy, Merz pointed out.
“Women with certain types of cardiovascular disease are at high risk of maternal [mortality] and morbidity,” said Lewey. “For these individuals, pregnancy may increase cardiovascular risk to a greater extent than certain forms of birth control.”
Because both pregnancy and birth control can be risky, women with known heart health issues should spend time assessing all options with their doctors, she emphasized.
Julia Landwehr
Julia is the associate news editor for Health, where she edits and publishes news articles on trending health and wellness topics. Her work has been featured in The Heights, an independent student newspaper at Boston College, and Minnesota Monthly.
learn more
Read more:
This story originally appeared on: Health News - Author:Kristen Fischer
