US girls got their first periods increasingly earlier over the last 50 years, new study finds

The study found that women born in the oldest bracket, between 1950-1969, got their period at 12.5 years old on average, compared to 11.9 years old for the youngest group, born between 2000-2005. Photograph: SDI Productions/Getty Images

Girls in the United States had their first periods earlier over the last five decades and it took longer to experience regular cycles, a new study has found.

The study, published in JAMA Network Open, found the trend is especially pronounced among Black, Hispanic, Asian and mixed race participants, and among those who reported lower socioeconomic status.