Hormonal birth control has allowed millions worldwide to manage their menstrual cycles and control their reproductive futures.
But as with any drug, there are pros and cons for doctors and patients to carefully consider.
While strong evidence suggests that hormonal birth control provides numerous benefits, some scientists argue that there are potential risks, like depression or stroke, that have been "inadequately addressed".
One concerning connection that keeps popping up in observational population studies around the world is the development of a rare yet treatable brain tumor called meningioma.
Researchers at the Danish Medicines Agency have now combed through 25 years' worth of health data in Denmark, covering roughly three million females, to clear up the picture.
Their findings are published in JAMA Network Open.
The nationwide study is the first of its kind to show that only certain types of contraceptives are indeed linked to this type of tumor.
Although the relative risk reported by the study is modest and the absolute risk is probably tiny, it is important to investigate further.
Injectable birth control called medroxyprogesterone (brand name Depo-Provera) showed the strongest association with meningioma tumors, with a relative increase in risk of about 4-fold.
According to the Danish study, weaker associations exist for combined oral contraceptives and the mini-pill, with a relative risk increase of 1.5-fold.
Importantly, these risks only persisted while participants were actively using contraception. The elevated risk generally seems to disappear within five years of stopping a contraceptive progestogen.
"While a 4-fold relative increase in risk seems very high, the absolute risk of meningioma is small," explains cancer epidemiologist Paul Pharoah from Cedars-Sinai Health Sciences University in the US.
He explains that about 5 women per 1,000 will develop a meningioma in their lifetime.
That only increases to 6 women per 1,000 women using medroxyprogesterone from ages 25 to 44.
"These very small increases in risk need to be balanced against the benefits of different forms of contraception," says Pharoah.
"It is important that women do not stop using their birth control pills without consulting their doctor."
Not only are meningioma tumors rare, but when they do occur, they are also typically benign in roughly 90 percent of cases.
On occasion, however, these tumors can cause seizures and cognitive issues, so they are taken seriously. Meningiomas are usually removed surgically or treated with radiation therapy.
Thousands of women who say they were diagnosed with an intracranial meningioma after receiving Depo-Provera injections have filed lawsuits against Pfizer since 2024.
In December 2025, the US FDA approved a new label for the injection that warns customers of a possible connection to meningiomas.
Obstetrician and gynecologist Gino Pecoraro from the University of Queensland in Australia acknowledges that while those taking certain forms of contraception may be at a very small increased risk for meningioma, there are also risks to not using contraception, too.
Pecoraro points out, for instance, that "pregnancy in Australia carries a maternal mortality rate of 6.6 per hundred thousand, while the Australian five-year survival rate following meningioma diagnosis is greater than 90 percent."
While it's unknown what causes meningiomas, there is good reason to suspect that hormones like progesterone play a role.
In the United States and Denmark, women are more than twice as likely to be diagnosed with meningioma compared to men.
What's more, meningioma tumors also tend to grow more rapidly during pregnancy or when a patient is taking therapies with progesterone-like mimics.
"We have known for a few years that high-dose exposure to certain progesterone drugs increases the risk of meningioma," reproductive endocrinologist Channa Jayasena from Imperial College London told the Science Media Center.
"Meningiomas are tumors of the lining of the brain. Most meningiomas have receptors that can 'listen to' progesterone in the body, so it is plausible that any type of progesterone-like drug could slightly increase the risk."
Progestogens are synthetic compounds that mimic the natural hormone progesterone. They are used in some contraceptive injections, IUDs, combined birth control pills, and progesterone-only pills – sometimes called 'mini-pills'.
For years now, scientists have suspected that this hormone may be linked to meningiomas; however, previous studies have turned up mixed results.
Often, these analyses did not take into account current contraceptive use as opposed to past contraceptive use, and this may have muddied the results.
The risk seems to be erased when contraception is ceased, at least according to this recent Danish data crunch.
Gynecologist Melanie Davies, who was not involved in the current study, says that this new research confirms an association between progestogens and some brain tumors.
However, she adds, because meningioma is such a rare condition, these findings "should not put women off using progestogens, which are effective hormonal treatments for debilitating conditions and suit many women who require contraception."
Jayasena also points out that this study did not look at hormone replacement therapy, which uses much lower doses of progesterone, and "so is not expected to increase meningioma risk."
"Therefore," he stresses, "these results do not apply to women taking HRT."
An investigation into the association between progestogens and meningiomas is currently ongoing at the European Medicines Agency.
Related: When You Got Your Period May Impact Dementia Risk, Study Finds
"Prescribers should certainly be aware of the association," argues Pecoraro.
"This is further evidence of the importance of appropriate contraceptive consultations addressing risks and benefits of various means of contraception, taking place between prescribers and women, prior to writing a script or making a recommendation."
Women who have suffered brain tumors after taking the injections argue that patients should be warned of the possible risks.
The study is published in JAMA Network Open.
This article was fact-checked by Rachel Garner and edited by Rebecca Dyer. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.