Why girls are getting periods younger than ever before

Over the past few decades, the onset of menstruation has shifted from a "when I was 12" storyline to one where girls are hitting puberty younger — and often, with more unpredictable cycles. Recent research reveals troubling patterns: girls in the US are getting their first periods on average six months earlier than those born in the 1950s and 1960s.

But the real curveball isn't just the earlier arrival — it's how long it takes for those cycles to settle. In many cases, irregular patterns persist longer, raising questions about what's behind the change.

Historically, menstruation kicked in around age 12–13. However, recent large-scale studies place today's average closer to 11.9 years for girls born between 2000 and 2005.

Some populations — especially girls from multiracial backgrounds, and lower socioeconomic groups — show even steeper shifts. The takeaway: puberty is occurring earlier, and the timeline for normalcy is extending.

Biologically, that means the body moves from childhood toward reproductive readiness sooner, but without the full maturation and regulation that often accompany it. The result: more cycles that start erratically and fewer that immediately stabilise.

An earlier first period and delayed regulation have consequences. Medical literature links early menarche with increased risks of breast cancer, cardiovascular disease, and type 2 diabetes.

On the social‑emotional side, coming of age physically before one is ready mentally can drive anxiety, body image problems, and peer tension. A longer time to regular cycles also complicates tracking and managing menstruation for young girls, interfering with daily life and self‑confidence.

In short: Younger first periods and longer‑lasting irregularity aren't only a biological curiosity. They raise questions about how environment, lifestyle, and biology interact and how prepared we are for that interplay. For girls growing up today, the timeline has shifted. And for the adults supporting them, awareness and action matter.