Secular trend in the sexual maturation of southern Chinese girls.

In 1993, a cross-sectional study of sexual maturation of normal Chinese schoolgirls was performed in Hong Kong. The aim of the study was to obtain an up-to-date reference for normal pubertal development in Chinese girls. Breast development was assessed in 3749 girls aged 7-19 y, and pubic hair rating was assessed in 3745 girls. Menstrual status was recorded in 6467 girls over 6 y of age. The median age of onset of puberty as indicated by breast stage II or above was 9.78 (95% CI 9.70-9.85) y. The median age of onset of pubic hair development was 11.64 (95% CI 11.56-11.72) y. The median age of menarche was 12.38 (95% CI 11.98-12.78) years. Percentile values for the age at which each puberty staging appeared were constructed and incorporated into the height-for-age charts. When comparison is made with similar studies done in 1962 and 1979, a significant downward secular trend in sexual maturation is observed (p < 0.01). Except for breast development the downward secular trend in sexual maturation appears to be diminishing and may be coming to a halt in the Chinese girls in Hong Kong. Their median ages of sexual maturation are now among one of the earliest medians recorded in the world population studied.