Menarche (from Greek μήν moon + αρχή beginning)'s the first menstrual period, or first menstrual bleeding in the females of human beings. From both social and medical perspectives it's often considered the central event of female puberty, as it signals the possibility of fertility. Timing of menarche's influenced by both genetic and environmental factors, especially nutritional status. The average age of menarche has declined over the last century but the magn… (More on Menarche)