[Association between early-life factors and pubertal timing in girls].

Objectives: To study the association between early-life factors (including birth weight, method of birth, gestational age, and history of gestational metabolic disorders) and pubertal timing in girls.

Methods: The stratified cluster sampling method was used to select the girls in grades 2-3 and 7-8 from three primary schools and three middle schools in Guangzhou, China from March to December, 2019, and breast development was examined for all girls. A questionnaire survey was performed to collect the information on early-life factors.