Birth Control Is Linked to Blood Clots, Even for Nonsmokers

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NEWS FLASH: Hormonal birth control can cause strokes and heart attacks even if you’re young and don’t smoke!

Of course, this isn’t really news. It’s more like an old story that’s been buried and forgotten. Drug companies have so successfully mitigated the facts that even doctors often get confused.

The history of birth control and blood clots

When hormonal birth control first hit the market in the early 1960s, doctors from several specialties began noticing unwelcomed side effects in many of their young, female patients. Despite the many questions and concerns being posed by leading physicians, nothing seemed to tarnish the growing popularity of the new contraceptive. This led one world-renowned neurologist to muse that the Pill had been granted a sort of diplomatic immunity.

That changed in April 1968 when the British Medical Journal released the results of a retrospective study revealing a 7.5-fold increased risk of death from stroke in women taking the Pill. For many young women, this was their first time hearing anything other than glowing praise about the Pill. Still, spin-doctors for the drug companies immediately hit the media circuit to reassure women that birth control remained “remarkably safe.”

Evidence on the blood clot risks of birth control

As more studies continued to link the hormones contained in birth control to increases in blood clots and other related issues like migraines, strokes, heart attacks, venous thromboembolism (VTE), and pulmonary embolism, the drug companies eventually came out with lower-dose formulations and claimed the issues had been resolved.

The reassurances sounded feasible and helped calm the storm that suddenly surrounded the Pill, but the new illusion of safety wasn’t built on any kind of reality. In fact, here we are decades later, and the newest hormones may be among the most dangerous ever put on the market.

A 2009 study found that women taking hormonal contraceptives were five times more likely to suffer VTE than non-users. The numbers are even more unsettling for popular new, third- and fourth-generation hormones. A widely cited Danish study from 2011 showed that women taking these formulations faced at least twice the risk of VTE over women taking second-generation hormones, and well over six times that of non-users. And a systematic review published in 2019 estimated 300-400 U.S. women die yearly from birth-control-related cardiovascular events. 

The legal system offers further evidence of the dangers. Bayer Pharmaceuticals, makers of the popular fourth-generation brands, Yaz and Yasmin, has paid out over $2 billion to settle tens of thousands of blood clot related lawsuits, many of which ended in death.

Birth control companies downplay blood clot risk

With all this mounting evidence tying hormonal birth control to blood clots, how have the drug companies responded? They put up a smoke screen.

Once it became obvious they wouldn’t be able to deny the link to blood clots any longer, the drug makers pivoted to draw attention to one particular finding from many of the studies—that the risks were highest in women who smoked and/or were over 35. 

You could almost say they embraced it—turned it into a mantra, because focusing on this vulnerable subset created the impression that birth control is safe as long as you are younger and don’t smoke. They even managed to work this misleading approach into the black box warning carried on the drug labels of many combination oral contraceptives. The label reads:


Cigarette smoking increases the risk of serious cardiovascular events from combination oral contraceptive (COC) use. This risk increases with age, particularly in women over 35 years of age…”

Many health websites work to reinforce the storyline by explaining how smoking while taking birth control constricts blood vessels and hampers blood flow to the heart. While this is true, the way the narrative is framed completes the illusion for young women that they have nothing to worry about as long as they don’t smoke.

This distorted message has been highly effective, but it still pushes away smokers, and, in the end, that means lost revenue. It appears as though the drug makers recently added a new wrinkle to the story to further mitigate the dangers for smokers. Some ‘medical advice’ websites have started including a quantity with their safety statements, such as “The risk of myocardial infarction may be increased in women using OCPs, especially if smoking (more than 10 cigarettes per day)” or “Do not use the combined pill, patch, or ring if you are over 35 and smoke more than 15 cigarettes/day.”

This new twist will undoubtedly convince some women who smoke fewer than 10 cigarettes per day that they have nothing to worry about.

How doctors started thinking birth control has low blood clot risk

On the surface, the danger of perpetuating this version of truth is obvious. Millions of women could be using hormonal birth control, while being completely oblivious to the risks, but the problem runs much deeper.

Lisa Hendrickson-Jack, host of the Fertility Friday Podcast, said whenever she interviews a doctor she likes to ask them about their training, “I’m told that in medical school they are obviously taught about the risks, but they’re often taught that women who are over 35 and smoke are more likely to X, Y, and Z. So, that primes them to not think about that for younger women.”

Indeed, doctors often dismiss migraines and other warning signs in younger patients, with tragic consequences

The takeaway is to be fully aware of the true health risks before choosing to take any form of birth control. If you do decide to use pharmaceutical birth control and experience side effects related to strokes or VTE, be prepared to stand up for yourself if your doctor seems dismissive, because they could very well have been primed to think you are too young and healthy to be at risk.  

Mike Gaskins is author of In the Name of the Pill.