We need to talk about birth control. Specifically, we need to talk about what is and isn’t dangerous about it, as there’s a lot of misinformation going around lately thanks to a scathing takedown of NuvaRing in Vanity Fair (Danger in the Ring by Marie Brenner, January 2014). If you haven’t read it, the story was a heartbreaking tale of two women who died from blood clots after using the birth control device. The story wasn’t, however, a calm and considered look at the accurate science of birth control (which is why I’m not going to link to it here).

To get a better idea of whether or not the story was realistic, or unnecessarily fear-mongering, I spent almost two hours talking with Trent MacKay and Diana Blithe, respectively the Chief and Program Director of the National Institute of Health’s Contraceptive Discovery and Development Branch. Here’s what I learned: A basic understanding of how birth control works will quickly dispel any fears you might have about using NuvaRing — or any method of birth control for that matter. So. Let’s all take a deep, calming breath and talk about how uteruses work.

The first thing you need to know is that nearly all forms of birth control (except intrauterine devices (IUDs) — I’ll explain why later) have the potential to cause blood clots. This fact is not unique to any specific contraceptive method and it’s the only potentially deadly side effect of birth control. It also has very little to do with birth control. What it does have to do with is the body’s completely natural reaction to pregnancy, a state of being that birth control tricks your body into thinking it’s in.

Basically this all comes down to two hormones you’ve probably heard a lot about: progesterone and estrogen. They work together to make your period happen and their levels rise and fall throughout your cycle. Estrogen does lots of jobs in your body, but in the case of your uterus, its levels go up just before your period to make the walls thicker so a fertilized egg can stick and grow a baby. When you’re actually pregnant, increased progesterone stops your ovaries from releasing eggs. When its levels drop you go through withdrawal, which tells your body it’s time for your period.

Birth control takes charge of the rise and fall of these hormones. During the first three weeks of your cycle, your BC method of choice releases synthetic progesterone (called progestin) and high levels of estrogen into your system causing your body to respond as if it’s pregnant. When you go into the fourth week of placebo pills (or when you remove your patch or ring), your level of progestin drops, and you get your period.

Estrogen has another interesting effect. Let’s just pause and think about giving birth for a second. There is the potential for quite a bit of blood loss. A woman’s body needs a way to control this and ensure that she doesn’t lose any more blood than is necessary. So when a woman is pregnant (and for a short time after giving birth) high levels of estrogen in the body also helps the blood to coagulate. To clarify, estrogen doesn’t cause blood clots, it just makes the blood more likely to clot and prevents a pregnant woman from bleeding out when she gives birth.

Estrogen doesn’t cause blood clots, it just makes the blood more likely to clot in order to prevent a pregnant woman from bleeding out when she gives birth.

It’s because birth control mimics pregnancy that blood clots are possible when taking them. And, actually, the higher dose of estrogen in birth control is a contributing factor (at least, that’s what science suspects). It’s during the progestin-withdrawal stage that you’re at the highest risk of getting a blood clot. The Mirena IUDs, on the other hand, have no possible risk of blood clots because they deliver a constant, low dose of progestin and your body never transitions into the estrogen-only phase. But here’s the thing: you are at much, MUCH higher risk for blood clots if you are *actually* pregnant. In fact, your highest risk for getting a blood clot is after you give birth. So, in a sense, by preventing pregnancy, birth control actually protects you from the chance of having a deadly blood clot.

You are at much, MUCH higher risk for blood clots if you are *actually* pregnant.

But why aren’t women everywhere dying left and right from blood clots caused by birth control? Because blood clots are possible but highly unlikely unless you’re genetically predisposed to them. And that’s a very rare thing. Here are some numbers for you from the folks at the NIH:

- For all humans, the lifetime risk of dying in a car accident is 1 in 84. Keep that number in mind, because some perspective is important here.

- For all humans who never take any birth control and have no predisposition to blood clots, the rate of actually getting one is 1-2 people out of every 10,000.

- For women with no predisposition to blood clots, the rate of getting one while taking birth control is about 5 in 10,000. (Of those 5, only 1-5 percent actually die from said blood clot.)

- For women with no predisposition to blood clots, the rate of getting one while pregnant is about five to ten times higher than while taking birth control (depending on the study).

- For women with the genetic predisposition to blood clots, the risk of getting one while taking birth control is 1 in 500. That’s a scary number, but it’s important to know that only 5 percent of the entire human population (meaning men and women) actually have the genetic predisposition.

Here’s another thing that you should know about blood clots and birth control: if you are going to get a blood clot it will most likely happen within the first three months of taking the drug. Your risk drops off significantly after that, though there’s still a slight increased risk for about a year. So if you’ve been using your NuvaRing — or any birth control method — for many years now there’s no need at all to make a sudden, panicked change.

There’s one caveat to all this. When using the NuvaRing there is, in fact, a slightly higher risk than other methods of birth control for blood clots (about 7 people in 10,000 vs. 5 or 6 in 10,000 with other birth control). Scientists suspect, but aren’t sure, that it might have something to do with the burst of progestin in your system when you put the ring back in. Still, the slightly increased risk is negligible. And it’s much lower than the risk during and just after pregnancy (which is about 1 in 1,000). If you’re not predisposed to blood clots then it shouldn’t be a concern. And if you are, a contraceptive like the ring, the pill, or the patch aren’t your safest choice anyway. Plus, keep in mind that every birth control can have annoying, non-deadly side effects, like wacky emotions, that you should talk about with your doctor.

I should also note that there are lifestyle choices that can increase your risks for blood clots that have nothing to do with birth control or pregnancy. Smokers and obese women, for example, are at a much higher risk. And, in fact, doctors are completely divided about how to prescribe safe birth control to folks who fall into those categories.

But all those complicating factors (and Vanity Fair articles) aside, if you are healthy and not genetically predisposed to blood clots then NuvaRing, or any method of birth control, is a safe choice when it comes to the risk of clots.