Age at menarche in French Canadian urban girls

SummaryIn 1969–1970, a random sample of 1002 girls aged 10·5 to 15·0 from different socio-economic strata were interviewed in Montreal schools. The mean age at menarche of these urban girls was 13·08±0·04 years (S.D. 1·10) from probit analysis. French Canadian girls today commence menarche at about the same age as British girls and about 8 months earlier than Montreal girls three decades ago. Contrary to findings in most other populations (with a different level and way of life), French Canadian girls from upper socio-economic groups mature later than girls from lower socio-economic groups.Girls from large families or with more linear physique were older at menarche than others. Family size and the type of physique were independent factors. There was a close relation between social class and family size, and we consider family size to be one of the most important factors contributing to the different onset of sexual maturation of girls in different socio-economic strata.