A 12-year study of menarcheal age.

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Abstract
Data on menarcheal age were collected on girls admitted to the University College of Swansea over a 12-year period. It appears that the downward trend in menarcheal age ceased in girls born about 1946 (the 1965 student intake) and that an upward swing may have since occurred. This change in the secular trend is not due to the association of menarcheal age with family size or of position in sibship, or to changes in the regional composition of the student intake. The well established effect of physique remains, but there is no effect of socio-economic status as assessed by the Registrar-General's classification of the father's occupation.