Secular trends and urban-rural disparities in the median age at menarche among Chinese han girls from 1985 to 2019.

The median age at menarche among Chinese Han girls continued to decline from 1985 to 2019 but at a slowing pace in the last five years. Urban‒rural disparities gradually narrowed. Sexual and reproductive health education and interventions to prevent the decline in the age of menarche are needed, especially in rural areas.