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Why First Periods Are Coming Earlier Than Ever

It’s called early menarche—here’s what the experts say.

Why First Periods Are Coming Earlier Than Ever

First periods are happening earlier than ever—and we’re not talking just a few days. 

In 1840, the average age of menarche, or the first occurrence of a menstrual period, was 16 years old in the United States. In 1919, that average dropped to 14. As of 2020? National Health Statistics found that women in the United States had gotten their first period at 11.1 years old, on average, with some cases reporting menarche as early as 8. 

This phenomenon isn’t just local. Per the New York Times, various global studies confirm that “the age of puberty in girls has dropped [in dozens of countries] by about three months per decade since the 1970s.” With children entering puberty earlier across continents, pediatricians and other experts are all wondering the same thing: Why is this happening? And why is it happening so quickly? 

Spoiler alert: there’s no definitive answer, but there are some theories. Here’s a few on the table for discussion, and what experts are saying about them. 

Theory: Today’s children have a higher average BMI.

Some researchers suggest that earlier menarche is directly linked to an increasing BMI, or Body-Mass Index, among children in the United States. Now, BMI is a flawed indicator for several reasons, but experts have referenced data that shows increased leptin, or a protein produced by fat cells, ratchets up estrogen and progesterone production. For this reason, some pediatric researchers link childhood obesity to earlier pubertal processes, such as breast development and first periods.

But this theory doesn’t fully explain earlier menarche among American girls—and it doesn’t explain the global trend, either. In her deep dive for the New York Times, journalist Azeen Ghorayshi reported that while children in Denmark were experiencing earlier puberty, the country’s average body mass index hadn’t increased in over twenty years. Pediatric endocrinologist Dr. Natalie Shaw, interviewed for the same article, stated: “Obesity doesn’t explain all of this. It’s just happening too quickly.” Many physicians are also firm that the relationship between obesity and early puberty is one of correlation, not causation. So, while a higher average BMI may be one piece of the puzzle, it’s definitely not the whole picture. 

Theory: Today’s children are exposed to more chemicals. 

Leading pediatric researcher Dr. Frank Biro is among those that consider exposure to endocrine-disrupting chemicals (EDCs) as a leading factor in early menarche. EDCs wreak havoc on the endocrine system in many ways: changing hormone levels and the way our bodies store them, altering our level of sensitivity to certain hormones, and even tricking the body into thinking they are hormones. And they’re just about everywhere: soy-based food sources, plastics, deodorants, sunscreen—you name it. One of the major (and most prevalent) EDCs? Industrial-grade chemicals.  

Pinning the tail on chemical exposure isn’t a huge reach. The dawn of industrialization does, in fact, line up with when we started seeing periods come earlier. And after finding that girls from low-income communities are more likely to menstruate earlier, researchers from UCSF suggested this could be due to their proximity to air pollution sources—like major roadways, factories, and plants that use industrial-grade chemicals. But, the jury’s still out on this one.

Theory: Today’s kids are stressed. 

It’s a harder time than ever to be a kid. Whether it’s the pressures of social media, increased awareness around climate change and its effects, the rise in U.S. school shootings, or the COVID-19 pandemic, youth today are dealing with unprecedented levels of stress. And according to some experts, it could be the reason they’re entering puberty earlier. 

Stressors like abuse, neglect, and other forms of trauma have been directly linked to earlier periods. In 2006, Dr. Marcia Herman-Giddens suggested that “high cortisol levels” activate the pituitary and adrenal glands, both essential in producing the hormones necessary to jump-start pubescent development. And for many children, stressors are everywhere—including behind their phone screens. A 2022 study by Pew Research Center found that 46% of teens in the United States have been abused online, including offensive name-calling, physical threats, and sexual harassment. 

Another major stressor? Poverty. Research led by Dr. Robert Hiatt studied over 1,000 girls across the United States and found that “lower socioeconomic status” was a major indicator for earlier menarche; additional studies in the United Kingdom, India, Peru, and Vietnam arrived at the same conclusion. If we consider that 160 million children live below the poverty line around the globe, perhaps stress-induced early puberty makes sense.  

So, what do we do?

If reading this sent you into a fear spiral about the future, you’re likely not alone. Yes, periods coming earlier on a global scale can be alarming—and early menarche is not without its risks. But while experts investigate further, it’s important for us to keep sight of what the data is saying right now: a bodily process is simply happening earlier. Though we don’t yet know why, the question is: how can we support those experiencing these changes for the very first time? 

If you’re a concerned parent, family member, or loved one, there’s plenty of info out there on supporting a child through early menarche and precocious puberty. Some guardians are having early-stage conversations about menstruation with their children. Others are seeking counsel from pediatric endocrinologists, their family pediatrician and other medical professionals. Whatever you choose to do, trust that you’re doing the best you can. 

While we can’t just slide a copy of The Care and Keeping of You under a tween’s door any longer, first-time menstruators still need our support. Whether it was a good memory or a mortifying one, you’ll likely never forget your first period—and the people who were helping you through it.

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