The first time I saw a neurologist for my migraines, she told me to stop taking birth control pills right away. Because I get sensory disturbances called auras with my migraines, she said, the pill—any pill—increases my stroke risk enough to be unsafe. Her advice meshed with the recommendations of the Centers for Disease Control and Prevention, which deem combined oral contraceptives—common birth control pills containing both progestin and estrogen—an "unacceptable health risk" for women who get migraines with aura. I took my doctor's advice and switched to an IUD, but that's when my migraine problems took a turn for the worse.

In addition to my typical aura migraines, which swarm my vision with pulsating zig-zag lines, I started getting migraines once a month that robbed me of my memory. Each time they hit, I was unable to remember what month or year it was, how old my kids were, what time I needed to meet my son's school bus—even how to use the remote control for the TV.

Alarmed, I dug into the research on migraines and discovered something surprising: According to a recent analysis published in the journal Headache, many of today's birth control pills are not only safe for women who get any kind of migraine, but they can also help prevent the most debilitating types—which would help explain why mine got worse when I went off the pill. According to this paper, the CDC's sweeping recommendations against the use of any combined oral contraceptive are based on a flawed, out-of-date interpretation of the science.

There's no question that birth control pills of yore were dangerous for many women. The first contraceptive pill, Enovid-10, which was first approved by the US Food and Drug administration in 1960, contained 10,000 micrograms (μg) of the progestin norethynodrel and the equivalent of 88μg of the synthetic estrogen ethinyl estradiol—which means that women back then got dosed with more progestin in a single day's pill than they do now in an entire 28-day pack, and more synthetic estrogen than women now get in four days' worth of pills. It soon became clear that these mega-doses weren't safe, increasing the risk for pulmonary embolism, deep vein thrombosis, heart attacks, and strokes. Since migraine sufferers were known to already be at a higher-than-average risk of stroke, these women were told to avoid combined oral contraceptives.

But most of today's birth control pills are different, because pharmaceutical companies have steadily lowered the hormone doses to make them safer. Today, 99 percent of the birth control pills taken by American women contain less than 50μg of the synthetic estrogen ethinyl estradiol; many contain 20μg or less. (It is the estrogen in the pills, rather than the progestin, that's tied to higher stroke and heart attack risk.) In fact, some women are prescribed pills that don't contain any estrogen at all.

Yet while the birth control pill has drastically changed, research on its safety—particularly for the one out of every five American women who gets migraines—hasn't caught up. This is the argument that Anne Calhoun, a headache specialist at the Carolina Headache Institute in Durham, NC, makes in her recent paper, which was published online in October. Scientists who evaluate birth control pill risks, Calhoun says, aren't always careful to exclude the pills that are no longer available or infrequently prescribed, so their analyses are seriously skewed. As an example, Calhoun points to a 2016 systematic review published by CDC researchers that concludes that combined oral contraceptive use is associated with two to four times the risk of stroke among women with migraines.

This finding was based on the results of seven studies, some of which linked the pill to higher stroke risk among migraine sufferers and some of which didn't. Of those that did, most only found a higher stroke risk among women who took formulations of pills that contained 50μg or more of the synthetic estrogen ethinyl estradiol—the pills that are rarely prescribed anymore. Calhoun concedes, too, that pills containing 30 to 40μg of estrogen, which still exist but are also infrequently prescribed, roughly double stroke risk among migraine-with-aura sufferers and should not be used.

But she points out that "many articles confirm that there is no increased risk of stroke with 20μg pills," which include Yaz and Aviane, Calhoun says—and there's no reason to think 10μg pills like Lo Loestrin Fe are unsafe. (That said, women over 35 who smoke, or women who have other risk factors including heart or vascular disease, should still not take any combined oral contraceptive.)

Yet the CDC still says that women who get migraines with aura should avoid all oral contraceptives, just in case. "Although there is little published evidence on risk of stroke among women with migraine with aura who use combined hormonal contraceptives," says Naomi Tepper, a physician scientist in the CDC's Division of Reproductive Health and a co-author of the systematic review, "there is concern that use of estrogen among these women would further elevate their already increased risk of stroke." Tepper points to a paper published in 2015 by researchers in China, who analyzed published evidence and concluded that even 20μg formulations might raise stroke risk.

But the authors did not include any information about the studies they analyzed to come to this conclusion. Neither Tepper nor Calhoun were sure which studies they analyzed, either, and the paper's authors did not get back to me when I reached out to them twice for more details. Finally, and rather importantly, the Chinese analysis assessed stroke risk among women in general who take birth control pills, not specifically among women who get migraines with aura.

It's also important to keep in mind that even if a drug does increase a woman's stroke risk, that doesn't mean that she is likely to have one. Let's do some math: Each year, 11 out of every 100,000 American women of childbearing age suffer a stroke. When women get migraines with aura, their risk is slightly more than doubled—about 24 out of every 100,000 young US women who get migraines with aura suffer strokes each year.

Even if a 20μg birth control pill does increase a woman's risk by an additional 50 percent, as the Chinese paper suggests, her stroke risk each year on the pill would then be 36 in 100,000, or 0.036 percent. Certainly, any increased risk is undesirable, but compare this overall risk to a woman's risk of being diagnosed with breast cancer before the age of 40, which is 0.57 percent—a likelihood 16 times higher. Recent large studies have also linked birth control pill use to a reduced risk of ovarian and endometrial cancer, so the pill may provide some health benefits, too.

Bizarrely, data also suggest that the right birth control pill can reduce the frequency of the most debilitating migraines. About half of women who suffer migraines get intense "menstrual migraines" a few days before their period—these are the ones I have been getting—precipitated by the drop in estrogen that occurs right before menstruation. "For several days out of the month you just lose your ability to function well, but with the right oral contraceptive pill, it just all goes away," says Stephanie Faubion, director of the Women's Health Clinic at the Mayo Clinic in Rochester, MN.

The best pill types for controlling these menstrual migraines are continuous formulations—packs that don't include placebo pills—such as Amethyst or drugs like Lo-Seasonique, which only have small estrogen drops four times a year. Unfortunately, very few doctors realize that menstrual migraines can be controlled this way; neurologists don't like to prescribe birth control pills, and gynecologists typically don't know much about migraines, Faubion says, so "women are kind of left in this no-man's land."

One thing is for sure: The studies that link high-estrogen birth control pills to strokes don't apply to the low- and ultra-low dose formulations that are popular today. And while the science on oral contraceptive safety could certainly benefit from more careful studies on how these lower-dose formulations affect women who get migraines with aura, there's little reason to think that pills containing 20μg or less of synthetic estrogen pose a substantial risk. As with any medical intervention, women should weigh the potential risks against the possible benefits—and migraine sufferers may get more relief from the right kind of pill than they realize.