[Age at onset of menarche: Results from the French Health Behaviour in School-aged Children study]

To describe age at onset of menarche in a large nationally representative sample of French schoolgirls.

Age at onset of menarche was assessed in the Health Behaviour in School-aged Children French cross-sectional survey. Data were collected in 2006 by anonymous self-reported standardized questionnaire. Median age at onset of menarche was estimated using Kaplan-Meier's method from a nationally representative sample of 2323 13 and 15 years old girls in school classrooms. Mean and standard deviation was also reported in the 1059 15 years old girls who had already experienced menarche.

Median age at onset of menarche was 12.8 years (interquartile range: 12.0-13.6), as was mean age at onset of menarche (standard deviation 1.2 years).

Age at onset of menarche and its variability (as measured by standard deviation) have decreased in most developed countries and seems stabilised at 13.0+/-0.5 years: our results are in line with this trend. The age limit of 9 years seems more coherent to define early menarche in French girls. These results may have an important impact on medical management of early pubertal development.