Three-thousand two-hundred seventy-eight school girls in Hong Kong, all of Southern Chinese origin, were carefully divided into high, middle, and low socioeconomic groups. The occurrence of menarche and the development of the breast, pubic hair, and axillary hair were investigated. The mean ages at which these traits of sexual maturation occurred were calculated by probit analysis. The various mean ages, in the order of high, middle, and low socioeconomic groups, are as follows: the first sign of breast development, 9.93, 10.22, and 10.65 years; the first appearance of the pubic hair, 11.63, 12.20, and 13.05 years; the menarche, 12.51, 12.75, 13.25 years; and the first appearance of axillary hair, 13.10, 13.45, and 13.74 years. The differences between these means of the three socioeconomic groups are all highly significant, as shown by the t-tests. Generally speaking, the breast develops 2½ years before menarche, the pubic hair appears half a year before menarche, and the axillary hair emerges half a year after menarche. The development of the breast and of the pubic hair were assessed according to the four-stage and the five-stage scores respectively, and the mean stages were calculated for both traits in each age group. Both the breast and the pubic hair showed steady advancement in the mean stages with age up to 19 or 20 years. When the girls of each age group were divided into groups according to whether they had or had not menstruated, the mean stages of both the breast and pubic hair development were always higher among girls who had menstruated.
Comparison of the mean age of menarche with that in some other countries indicates that our girls are among the very earliest ones to mature. The possibility of the presence of a secular trend in the mean ages of attaining sexual maturation of Chinese girls is discussed.
- Received February 18, 1963.
- Accepted March 27, 1963.
- Copyright © 1963 by the American Academy of Pediatrics