What We Still Don’t Know About Heavy Flow

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A lot of people assume their periods are normal even when they’re not. Bleeding disorders and abnormal bleeding can run in families, and if your mother, sister, or aunt have all experienced extremely heavy bleeding, it can seem like that’s what normal is. As Dr. Bethany Samuelson Bannow, hematologist, researcher, and professor at Oregon Health & Science University, puts it, “I always say, ‘Believe everything a woman says unless she tells you her periods are normal.’”

Officially, “normal” is a period that lasts two to seven days and occurs once a month with total blood loss ranging between 30 milliliters and 50 milliliters (roughly between one and two ounces). (Bleeding for more than seven to 10 days is generally too long, and bleeding in between periods, after sex, or after menopause is also abnormal.) Blood loss of more than 80 milliliters is associated with higher rates of iron deficiency and is a general benchmark that can indicate heavy menstruation.

You might have to decide if your own flow is “heavy” or “light” when selecting a box in the tampon aisle, but different products and brands may have their own definition of heavy. Tampons are the only period products that have industry regulations around the amount of liquid they can absorb. (These regulations came after the toxic shock crisis of the 1970s, when hundreds of women became sick at the start of their periods after using a superabsorbent Procter & Gamble tampon made of synthetic material.) That means the amount of liquid that light-, medium-, or heavy-absorbency tampons can hold remains consistent across brands and is generally advertised right on the box. It also means that other period products don’t have to follow those benchmarks, leaving consumers to figure it out for themselves. While pads, tampons, and menstrual cups generally hold similar amounts of liquid, according to findings from a recent study by Bannow, their maximum capacity can vary between product and brand. That means comparing a tampon to a pad to period panties to a menstrual cup is not necessarily a one-to-one translation. And to make matters even more complicated, companies determine these amounts by using saline, not blood — two very different materials that can be absorbed at different rates.

There’s also the question of, well, how do you know how much blood you lose during a period? How would a person even begin to answer? What does 30 milliliters of blood — or 50, or 80 — over the span of a week actually look like in the course of someone’s daily life? It turns out, scientists and doctors may not actually know.

That lack of knowledge can have serious consequences for the one-third of menstruators who experience heavy bleeding. Heavy bleeding can be uncomfortable and untenable and it can also indicate structural issues, like polyps or fibroids, or nonstructural issues, like a hormonal imbalance or endometrial cancer. It’s associated with endometriosis (when endometrial tissue grows outside of the uterus), adenomyosis (when endometrial tissue grows into the wall of the uterus), and perimenopause (the time around menopause when your ovaries gradually stop releasing eggs). But if you don’t know when your period is heavy, and doctors don’t know the right questions to ask to find out, people could be unaware of issues they need to address. Or when a patient does bring it up, miscommunications can lead to misunderstandings about how much blood they are actually losing.

In some cases, heavy menstruation can be an indicator of a blood disorder. Certain blood disorders are more likely to be symptomatic in people who menstruate simply because that is already a regular occurance, Bannow says. Other symptoms of blood disorders can include easy bruising, prolonged bleeding after cuts, or nose bleeds that continue into adulthood. Unmanaged blood disorders can lead to chronic illness. Some blood disorders can also lead to higher risk of blood clots or heart attacks, while others can lead to excessive bleeding — which can be especially dangerous after childbirth, after surgery, or after certain injuries, like a car crash.

While heavy menstruation is a symptom associated with such issues, it’s also its own diagnosis. If bleeding is so heavy it disrupts your life — emotionally, socially, or physically — then that is considered too heavy, and you can get treatment. Depending on the cause of the heavy bleeding and the patient’s goals, treatment can include birth-control pills or a hormonal IUD. Tranexamic acid is a nonhormonal treatment that a patient can take at the start of their cycle to lessen menstrual bleeding. Surgical options can also be used to remove things like fibroids or polyps, which can sometimes cause heavy bleeding. Endometrial ablation (a procedure to remove the uterine lining) and a hysterectomy (a surgery that removes the uterus entirely) can be used as treatment for heavy periods, but they also end a patient’s fertility. Heavy bleeding can be especially worrying if blood loss makes you feel lightheaded, you pass out, or you have iron-deficiency anemia. In severe cases of heavy menstrual bleeding, a patient may need a blood or iron transfusion.

It can be important for a doctor to understand how much blood a patient loses during periods to know if they’ll need further treatment. Bannow says there is a form that patients can fill out, often used in research, that illustrates the saturation of menstrual products and how often they are changed to help find out how much blood is lost. “But when a patient comes into my clinic, I don’t want to be like, ‘OK, take this form home and come back in two months and I’ll talk about how to help you then,’” she says. “I want to get down to the nitty gritty right then.”

To assess blood loss, sometimes providers need to ask pointed questions to find out what “normal” or “heavy” bleeding actually means to a patient. Kristin Riley, a doctor who specializes in chronic pelvic pain and endometriosis, says she has patients come in and often say they have to miss work or school, they don’t leave the house on a day when their period is particularly heavy, or they bring an extra change of clothes everywhere they go. For her, that indicates bleeding is abnormal. Once it’s established that bleeding is abnormal, you’d think adding up tampon use over a certain amount of time could add up to the amount of blood lost. But because companies use saline to determine absorption instead of blood, and because patients don’t all use tampons or pads, the actual amount of blood loss can remain elusive.

Bannow’s study measured the absorption of different period products to see how much blood they could actually hold. Her team measured tampons and pads but also modern period products like menstrual cups and discs and period panties. The study is the first to include all of these types of products and measure their capacity with blood instead of saline. They found that on average, menstrual discs can hold the most blood — at 60 milliliters, about three times more blood than an average heavy tampon or pad, which can hold 20 to 50 milliliters. This means that if a patient changes their disc three times a day, that could equal a much higher blood loss than if someone says they change their tampon three times a day.

Bannow also found that certain tampons could actually hold more blood than saline. This is important because people may be losing more blood than they think if they measure blood loss by how many tampons they are using in a day. “We’ve sort of co-opted these products, which aren’t meant for diagnostic purposes, to use in our diagnostic algorithms,” Bannow says.

Historically, much of the scientific research of periods has been tied to fertility, and whether a person could still have a baby. “Generally, heavy periods and pain and discomfort around menstruation have often been considered women’s burden to bear,” says Rachel Gross, author of Vagina Obscura: An Anatomical Voyage. “They haven’t been the subject of serious scientific inquiry in the past.” This has left a large gap of understanding on what heavy periods are and how to treat them.

A shifting understanding of the uterus to see it as a regenerative organ that heals itself scarlessly each month — not an organ just meant for fertility, but an integral part of the entire body — opens up research and treatment for all kinds of diseases, not just uterine disorders. “We have this organ that literally bleeds every 28 days for 48 years, but we have no idea how the blood coagulates there,” Bannow says. The full process of how the uterus stops bleeding is still understudied, but it could have widespread implications for people who have periods and those who don’t.

For all that modern science has learned about heavy menstruation, plenty of questions remain. It can be frustrating, Riley says, to still have unanswered questions about things like fibroids, which affect 70 to 80 percent of people with periods and can cause heavy periods. For some people who have heavy bleeding, the cause remains unknown — all their tests come back normal. “We’re just understanding how menstruation works as a nonpathological event, which means that we have the basis to understand heavy periods and when things go wrong in this process,” Gross says. With more studies like Bannow’s that take menstrual bleeding seriously, maybe it will be possible soon for someone to not only know when they need treatment for blood loss during their period — but also which box of tampons to pick up at the store.

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What We Still Don’t Know About Heavy Flow