Menarche is occurring at younger ages in the U.S., especially among racial minorities and lower-income groups. This trend has raised concerns, prompting scientists to investigate its underlying causes.

When Are Girls Getting Their First Period: The Study

Girls are starting their periods at younger ages, with cycles taking longer to regulate—raising health concerns.

The Apple Women’s Health Study analyzed data from 71,341 participants (1950–2005), categorizing menarche as very early (before 9), early (before 11), and late (16+). Findings showed fewer girls achieving regular cycles within two years.

Researchers also examined BMI at menarche, revealing potential links to this concerning trend.

Study Findings on Early Menarche

Research shows a steady decline in the age of first menstruation across generations. Girls today not only start their periods earlier but also take longer to establish regular cycles. The rise in early and very early menarche is most notable among those born between 2000-2005, particularly in racially diverse and economically disadvantaged groups.

What’s Causing Earlier Periods?

Key factors include diet, stress, childhood trauma, and environmental toxins. However, the strongest link is with BMI—childhood obesity significantly increases the risk of early puberty. These factors also affect period regularity, pain levels, and even menopause timing, impacting long-term health.