Do Girls Get Their First Periods Sooner Than Before?

We live in an era in which generation gaps are not just psychological and cultural, but also biological. How many of us haven't compared our younger selves to children of the same age and thought about how strange "kids these days" are in their habits, behavior, and personalities? One of the most striking differences we perceive between ourselves and younger generations is the tendency toward early puberty. According to the perceptions of many, girls now get their first periods far sooner than girls in generations past. But is this true?

Long-Term Changes

There are certainly long-terms changes in the age at which girls enter puberty and begin menstruation. There is a well-documented decline in the average age of menarche (a girl's first period) between 1850 and 1960. In 1850, clear documentation notes that average European girls began menstruating at around age 17-- an age now considered almost alarmingly late. In 1960, however, European girls were getting their first periods at an average age of thirteen.

Short-Term Changes

Modern shifts in the age at which girls begin menstruating are far less remarkable than the changes documented between 1850 and 1960. However, there is some documentable difference. In the 1960s, girls got their first periods at an average age of 13. This age fell to 12.91 in the 1970s, gradually declining to its current median of 12.43. Although there is some change in the average age of menstruation, it isn't quite as pronounced as we often perceive.

Factors Causing these Changes

Girls do not generally begin menstruating until they have achieved sufficient body fat-- usually about 17% of the volume of their bodies. In the 1800s, when malnutrition was common, it was rare for girls to have this amount of body fat before the mid-to-late teenage years. Today, rising obesity rates have enabled girls to reach puberty far sooner than in antiquity, and slightly sooner than in the recent past. Some experts have theorized that environmental exposure to estrogen and estrogen-like compounds, as well as cultural factors, might also play a role in the onset of puberty for girls.

What Influences Our Perception

Many parents will swear that our daughters are reaching puberty far earlier than our own generations did. We hear of ten- and eleven-year-olds getting their first periods and feel shocked-- certain that this didn't happen back in our day (when, in fact, it did). Our perceptions are often influenced by the shock of our own aging and our children's maturity. We struggle to believe that our children are old enough to reach puberty and justify this shock by telling ourselves that the world was very different just a couple of decades ago. Ultimately, though, while there have been shifts in the onset of puberty, the difference is not quite as marked as we often believe it is.

References Used:

Journal of Obesity. 2011;2011:180729. Epub 2011 May 18.
Pediatrics. 2003 Apr;111(4 Pt 1):844-50
Pediatrics. 2003 Jan;111(1):110-3.