Momma Data

Debunking the latest studies about children's health and well-being

Playdate with Puberty:The Evidence Behind Early Puberty

Are girls really starting puberty earlier than ever?

Girls sprouting breasts in first grade, periods in third grade. Elizabeth Weil’s recent piece in the New York Times Sunday magazine, The Incredibly Shrinking Childhood, featured a 6 year-old with pubic hair. It’s enough to make any parent start wondering what’s in the water. The media routinely declares girls start puberty earlier than ever. Recently I ran into a rather well-known pediatrician who said no question she’d been seeing girls maturing sooner in her practice. Ask your pediatrician, friends, the school nurse, they probably agree, mine all do. Earlier puberty now seems to be a foregone conclusion.

 Before stocking up on Kotex Tween you might want to check out the evidence.

 If we’re going to talk about girls entering puberty earlier we best go back in history. First stop is the Museum of Menstruation to see one of the first official records in the US documenting age of menarche or first menstruation. According to the Medical News published in 1901 a Dr. G. J. Engelmann presented a paper at an American Gynecological Society meeting in which he reported American-born girls start menstruating at age “13.9 or 14.” He and “his friends” had collected menstrual histories of some 1,000 women.   

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Now fast forward to pediatrician James Tanner and his seminal 1962 book, Growth at Adolescence.  A lot of our knowledge about pubertal timing comes from Tanner’s work in Britain circa Post- WWII, specifically children living in an English orphanage starting in 1948. Tanner originally planned on studying malnutrition but ended up documenting not only physical growth but sexual development, ultimately giving the world The Tanner Scale, a pictorial and descriptive guide to what he perceived as the stages of puberty. As much as I’d like to forget the creep factor of some man meticulously photographing naked orphans, I can’t because today the medical profession continues judging what’s normal partly based on the bodies of 192 likely malnourished, possibly traumatized working-class girls who’d survived a war.  

Tanner declared girls start developing breasts on average at 11 and menarche at 13. Based on his own small, selective sources (e.g., poor country girls, orphans) he also calculated age dropped from 17 in the mid-1800s to 12.8 in 1962 or about 4 months per decade, a finding that fit quite nicely with his conclusions kids gradually were getting taller and heavier. For the most part we’ve taken his word for it. Common wisdom held the age of onset declined from the 19th to late 20th century mainly due to improved nutrition and lifestyle. 

Nobody bothered much with the timing of puberty until a large 1997 US study showed girls getting boobies earlier than previously expected. Breast buds appeared in white girls at average age 9.96, black girls, 8.87. Moreover, 5% of white girls had buds at 7 years old. Cue surprise. More studies. Evidence about the timing of menarche not to mention breast development was slim pickings before this point. 

More worry ensued in 2010 when a US study showed breast buds by age 7 in 23% of black girls, 15% of Hispanic girls, 10% of white girls and 2% of Asian girls. As troubling as this trend in breast development may seem, some worry that we simply don’t have enough good baseline data. Others question whether it’s a sign of early puberty. A handful of studies suggest it’s not accompanied by the normal hormonal activity and might be attributed to obesity.

The case for menstruation? Even messier. The 1997 study that set off the current breast brouhaha found no such change in menarche. Dueling 2003 studies published in the journal Pediatrics yielded two slightly different conclusions but roughly the same age of onset. The first found the median age (12.43) didn’t differ significantly from a 1973 estimate (12.77). The second reported age significantly declined from 12.75 to 12.54 but had an earlier time frame.  While most experts agree breast development is occurring earlier opinions still vary about menstruation.       

Frankly I expected more data and more agreement considering the degree of certainty out there. Sure, assessing phenomena over time is always tricky. The empirical evidence here is no exception with different researchers studying different populations on different continents with different measures and thus a bevy of different conclusions. There’s also the problem of explaining ancient history like the records of girls aged 12 and 13 getting married and preggers in long-ago civilizations like the Roman Empire. Early Jewish custom also had tweens betrothed at 12, married and with child soon thereafter. It’s not like tweens today invented early puberty. 

If we can’t agree on whether girls start puberty earlier we are far from explaining why. Of course we dread the usual "environmental" suspects, the endocrine disruptors like bisphenol-a and phthalates that have been linked to cancer, heart disease and other ill health in both animals and to a lesser extent, humans. In addition to a slew of social cultural factors (e.g., living with a single parent, a step-father, early life stress), research has also linked obesity to earlier maturation.  

And I haven’t even mentioned  the effects of starting puberty earlier or otherwise…another discussion altogether.   

Puberty at any age is a challenge for most parents. Hype over earlier puberty makes it even more difficult to stay calm. Let alone positive, the current recommendation.  Somehow you must communicate the message puberty is a normal part of life and not proof your child’s health and well-being has been compromised for decades to come by potential carcinogens, a dysfunctional home or a diet high in fat and refined carbohydrates. 

Good luck.  

Polly Palumbo, Ph.D., is a former research psychologist and founder of Momma Data, a non-profit organization that tracks and fact-checks parenting media. more...

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