Age at menarche of schoolgirls in Egypt.

The mean ages at menarche of 1365 Egyptian girls attending eight different schools in the Cairo region and representing three strikingly different socio-economic sectors were estimated by probit analysis as 12.59 +/- 0.29 for the well-off girls in Cairo; 13.09 +/- 0.17 for the middle-class girls in Cairo; 13.89 +/- 0.18 for rural agricultural areas. The results were compared with those for some European series and with other data from Arabic-speaking countries in the Middle East. Egyptian well-off girls in Cairo have one of the earliest recorded means of all populations studied. In contrast, those from rural agricultural areas are delayed probably because of malnutrition and endemic diseases such as bilharzia, aggravated by the tendendcy for poor uneducated parents in agricultural societies to have large families.