[A study of developmental order of secondary sexual characteristics in Beijing girls]

A six-year (1980-1986) study of the developmental status of the secondary sexual characteristics was made among 937 girls in Beijing. The mean age of the first appearance of the secondary sexual characteristics was breast 11.84 +/- 0.95 years, pubic hair 13.29 +/- 1.11 years, axillary hair 13.71 +/- 1.21 years; the average age of developmental maturation was breast 13.95 +/- 1.16 years, pubic hair 14.85 +/- 1.29 years, axillary hair 15.14 +/- 1.24 years. Their developmental order, as measured by the mean values of the groups, was breast, the first menarche (12.88 years), pubic hair, axillary hair. But when the individuals were examined only 22.85% was found to be in accord with the above order. The individual variation was very great. The course of development took about 3.5 years, but some needed one year to develop others six years. Some girls developed and finished at the same time, some finished earlier or later. Only a few girls have had no development of pubic hair and axillary hair until 18 years old.