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World Health Organization multicenter study on menstrual and ovulatory patterns in adolescent girls. I. A multicenter cross-sectional study of menarche. World Health Organization Task Force on Adolescent Reproductive Health.

To study the maturation processes during puberty, the Task Force on Adolescent Reproductive Health of the World Health Organization implemented a multicenter study on the age of menarche. From seven centers in six countries, 3,073 girls between the ages of 11 and 15 years volunteered for a two-year study. The girls were questioned at entry as to whether they had menstruated; social background data were recorded, and height and weight were measured. The median age for menarche was calculated by a life-table technique. The median ages were: Hong Kong-12 years, 9 months; Geneva, Switzerland-13 years, 1 month; Zafed, Israel and Stockholm, Sweden-13 years, 3 months; urban Colombo, Sri Lanka-13 years, 6 months; Ile-Ife, Nigeria-13 years, 9 months; and rural Peradeniya, Sri Lanka-14 years, 5 months. Menarche of the rural Peradeniya girls was later than the urban girls from Colombo and other study centers. The mean heights, weights, and obesity indices (Quetelet's Index) were higher in postmenarcheal girls compared to premenarcheal girls for each age at all centers.