Primary amenorrhea is characterized by delayed menarche (the onset of menses during puberty). At puberty the first monthly period known as menarche marks the onset of menstruation. Isolated premature menarche is rarely the first manifestation of precocious puberty. The onset of menstruation (menarche) may be alarming to unprepared girls and mistaken for illness. The seclusion of girls at puberty (i.e. menarche) is another such custom. Initiation of ovulation after menarche is not inevitable. The initial flow of menarche is usually brighter than mature menstrual flow. Concentrations of maternal serum PCB and DDE and their daughters' age at menarche were reviewed. A number of traditions are associated with the earlier critical maturation point of menarche. In multivariate analysis, DDE but not PCB was linked with a lowered age of menarche. Post-menarche, the young woman enters a stage called maidenhood, the stage between menarche and marriage. The average age of menarche in the United States is about 12.5 years. The average age of menarche is 12 to 15. The average age of menarche is 12.5 in the United States. Limitations of the study included indirect measurement of the exposure and self reporting of menarche.