This could be a tough pill to swallow.
An estimated 250 million women worldwide are believed to use some form of hormonal contraception. Past research has suggested a link between the use of synthetic hormones to prevent pregnancy and an increased risk of stroke and heart attack.
Scientists in Denmark examined the risks associated with vaginal rings, skin patches, intrauterine devices (IUDs), implants inserted under the skin, injections, estrogen-progestin pills and progestin-only pills.
Hormonal contraceptives contain estrogen and progestin or only progestin to mirror the hormones that naturally occur in a woman’s body. Estrogen regulates the menstrual cycle while progestin is a synthetic version of progesterone, a hormone crucial for supporting pregnancy.
For their study, researchers tracked national prescription records over 25 years for more than 2 million Danish women between 15 and 49.
Women were excluded if they had a history of antipsychotics use, cancer, liver disease, kidney disease, polycystic ovary syndrome, endometriosis, infertility treatment, hormone therapy or other conditions.
After adjusting for factors such as age, education, high blood pressure and diabetes, researchers linked the estrogen-progestin pill — known colloquially as the birth control pill — to twice the risk of ischemic stroke and heart attack.
That translates to one extra stroke for every 4,760 women taking the pill for a year and one extra heart attack for every 10,000 women per year of use.
Ischemic stroke, when a blood vessel in the brain becomes blocked, is the most common type of stroke.
Estrogen-progestin contraceptives that aren’t pills, such as the vaginal ring and skin patch, were also associated with elevated risks.
The vaginal ring increased ischemic stroke risk 2.4-fold and heart attack risk 3.8-fold, while the patch raised stroke risk 3.4-fold.
Progestin-only products, including the “mini pill” and implants, fared better. The progestin-only IUD was the only contraceptive not linked to a higher risk.
The researchers emphasized that theirs was an observational study, so no firm conclusions can be drawn about cause and effect. There could have been other factors that spurred the strokes and heart attacks that they didn’t take into account.
“Although absolute risks [of these incidents] were low,” the researchers wrote this week in the BMJ, “clinicians should include the potential risk … in their assessment of the benefits and risks when prescribing hormonal contraceptive methods.”
In an accompanying editorial, Royal Institute of Technology postdoctoral researcher Therese Johansson noted that arterial thrombosis — when a blood clot forms in an artery, potentially leading to a heart attack or stroke — is rare in young women.
However, the side effects are serious and hormonal contraception use is widespread.
Johansson is calling for campaigns to increase awareness of the potential risks associated with various contraceptive methods.
“These initiatives should be supported by training for healthcare providers to ensure consistent and evidence-based counseling,” she wrote in the BMJ.
