Tanner stages of thelarche in relation to anthropometric and ultrasound predictors in premenarcheal girls.

INTRODUCTION: Thelarche is often the first sign of puberty initiation in girls. Although Tanner staging is widely used, it remains subjective. This study aimed to investigate the relationship between Tanner breast staging and anthropometric, breast ultrasound, and pelvic ultrasound parameters in healthy premenarcheal girls. MATERIAL AND METHODS: A cross-sectional study was conducted at Vilnius University Hospital Santaros Clinics (September 2023-July 2025), including 251 premenarcheal girls aged 7-13 years. Breast development was staged using Tanner criteria. Anthropometric and ultrasound parameters were recorded, including body circumferences, skinfolds, uterine and ovarian dimensions, and breast tissue thickness. Logistic regression identified predictors of pubertal stage, and model performance was evaluated using ROC analysis. RESULTS: A total of 251 girls (mean age 10.5 ± 1.8 years) were included. Thelarche (Tanner B2) occurred at a mean age of 10.7 years. Anthropometric parameters varied significantly across Tanner stages, with body circumferences demonstrating very large effect sizes, whereas skinfold thickness showed only medium effects. Pelvic ultrasound parameters exhibited even stronger associations with Tanner staging. In multivariable analysis, uterine body length (OR = 1.12 per mm, p = 0.004), uterine thickness (OR = 1.23 per mm, p = 0.003), left ovarian follicle count (OR = 1.39, p = 0.035), and right ovarian length (OR = 1.11, p = 0.013) independently predicted Tanner B2-B3 status, while a higher number of right ovarian follicles was inversely associated (OR = 0.72, p = 0.036). The logistic model accurately distinguished Tanner B2-B3 from B1, demonstrating excellent discriminatory ability (AUC = 0.924, 95% CI 0.889-0.959). CONCLUSIONS: Anthropometric and particularly pelvic ultrasound parameters are strong indicators of thelarche and early pubertal maturation. Our findings support the use of pelvic ultrasound as an objective, non-invasive adjunct to Tanner staging, especially in situations where visual breast assessment may be uncertain.