Abstract: Background Menarche is an important sign for girls to enter the late stage of puberty, and it is also the last opportunity for girls' height intervention. As menarche is affected by many factors and has great individual differences, correcting understanding and mastering the growth pretention and characteristics of girls at menarche can provide reference for the final height evaluation and intervention of girls with different menarche age in clinical practice.Objective To analyze the age, bone age (BA) and physical development characteristics of girls at menarche to explore the clinical evaluation method of predicting final height (PAH) after menarche.DesignCross-sectional survey.Methods We retrospectively collected the data of girls with menarche time, physical measurement and X-ray of bone age who visited the Department of Growth and Development of Children's Hospital Affiliated to Capital Institute of Pediatrics from 2008 to 2018. We excluded the cases with the interval between menarche time and visit time longer than 3 months, with clear diseases affecting children's growth and development, with clear etiology causing secondary central precocious puberty or peripheral precocious puberty, and those previously treated by growth hormone or Gonadotropin-Releasing hormone inhibitors. According to the inclusion and exclusion criteria above, three professional pediatricians screened medical records in paper or in electronic forms, extracted and chose data, and finally entered all selected data into Epidata database by a single person. The chronological age, bone age, HtSDS, HtSDS_BA, predicted final height (PAH) and predicted growth potential were calculated according to the pre-defined methods. The menarche age was divided by interval of 1 year, and the BA at menarche was divided by interval of 0.5 year.Main outcome measures BA at menarche, PAH and predicted growth potential.Results a. MA of 694 girls was 10.7±1.1 years and BA at menarche was 12.4±0.6 years. The average MA of different groups varied from 8.5 to 13.2 years, but the BA at menarche was stable, ranging from 12.4 to 12.8 years. b. The BA at menarche was closely related to their growth level. The youngest MA group had the most advanced BA and highest HtSDS. For example, the BA of 8-year-old MA group was 3.8±0.5 years advanced and their HtSDS was 2.60±1.32 while the BA of 13-year-old MA group was 0.7±0.7 years behind, and their HtSDS was -1.05±0.59. However, the average HtSDS_BA of different MA groups ranged from -1.17 to -0.68, with few differences between groups. c. The PAH-Ht of girls after menarche was 7.3±2.6 cm which was highly negatively correlated with BA at menarche (r=-0.960, P<0.001). The average PAH-Ht of girls decreased from 12.7 cm to 4.0 cm when the BA at menarche increased from 11.0 to 13.0 years (F=1,194.393, P<0.001). d. According to the formula of PAH we derived from this study (R²=0.992), we can calculate the cut-off point of height at menarche in accordance with different PAH. When the BA at menarche is 12 years, for example, the height at menarche should be higher than 139.8 cm with PAH higher than 150 cm, and the height at menarche should be higher than 151.3 cm with PAH higher than 160 cm.Conclusion The BA of girls at menarche is relatively stable. BA is a reliable index to predict menstruation and evaluate the growth level of girls. For girls after menarche, BA can also accurately predict their growth potential.

Key words: Menarche, Bone age, Height, Growth potential