Prediction of body mass index and skeletal maturity for early menarche risk at menarche onset: a cross-sectional study of Chinese girls.

BACKGROUND:This study aimed to assess the predictive value of body mass index (BMI) and skeletal maturity for the occurrence of early menarche in Chinese girls. METHODS:A cross-sectional analysis was conducted on 785 girls aged 8.1-14.6 years who visited our hospital within 3 months of menarche onset. Early menarche was defined as menarche age (MA) <10 years. Skeletal maturity was classified based on the difference between bone age (BA) and chronological age (CA), termed BA-CA; advanced BA was defined as BA-CA>2 years. RESULTS:The average MA was 10.7 (SD: 1.1) years, with a prevalence of early menarche of 23.3%. BA exhibited relative stability compared with MA, with an average of 12.8 (SD: 0.5) years at menarche onset. At menarche onset, the average height, weight and BMI were 149.1 (SD: 5.1) cm, 43.3 (SD: 7.2) kg and 19.4 (SD: 2.8) kg/m², respectively. Logistic regression analyses indicated that every 1-year increment in BA-CA was independently associated with a 18.90-fold higher risk of early menarche (95% CI 11.77 to 30.32), respectively, and remained statistically significant even after adjusting for height or mid-parental height. Furthermore, the prediction of BA-CA for early menarche demonstrated a dose-dependent pattern across BMI categories, with the greatest risk observed in normal-weight girls, the lowest risk in obese girls and an intermediate risk in overweight girls at the same degree of BA advancement. CONCLUSIONS:Our findings provide evidence supporting the significant contributions of BMI and skeletal maturity in predicting early menarche among Chinese girls at menarche onset. Additionally, the results suggest a dose-dependent relationship between skeletal maturity and BMI categories, with normal-weight girls displaying a higher risk of early menarche compared to overweight and obese girls with the same degree of BA advancement.