title: [Multi-center study of premature thelarche and gynecomastia in Chinese infants and toddlers].
abstract: OBJECTIVE
  The term "premature thelarche" refers to isolated breast development before 8 years of age in female, without any other signs of sexual maturation, while "gynecomastia" is the presence of breast tissue in males. This study aimed to investigate the prevalence of premature thelarche and gynecomastia in Chinese infants and toddlers, identify the potential risk factors, and explore the influence of early breast development on physical growth, mental development and psychomotor development.
  
  
  METHODS
  A total of 1 510 full term and healthy children at the age of 0-48 months were sampled by stratified cluster random sampling method from 8 provinces from 2011-2012. Weight, height and breast development were assessed by senior primary pediatricians, while Bayley Scale of Infant Development-I (BSID-I) was used to measure the mental developmental index (MDI) and psychomotor developmental index (PDI) for children aged 2-30 months. Social-demographic Questionnaires were completed by the caregivers.
  
  
  RESULTS
  The combined prevalence of premature thelarche and gynecomastia was 1.6% (23/1 475), girls 2.2% (15/695), boys 1.0% (8/780), all within 2 years of age. The birth weight, feeding patterns in first 4 months, delivery mode, weaning time and social economic status were not significantly associated with the breast development. However, lower father's education level (OR = 3.632, 95%CI = 1.565-8.432) as well as smoking mother (OR = 18.960, 95%CI = 1.590-226.304) were significantly related to breast development even after adjusting for potential confounders. Lower weight (-0.479 ± 0.648 vs. 0.005 ± 0.987, P < 0.05) and height (-0.602 ± 1.042 vs. 0.008 ± 0.986, P < 0.05) Z score were found in breast development group, even after adjusting for age, gender and father' education level. Neither mental development (t = -0.082, P > 0.05) nor psychomotor development (t = 1.054, P > 0.05) was associated with breast development.
  
  
  CONCLUSIONS
  We showed a similar prevalence of premature thelarche with the data reported in similar studies reported from other countries. Among the 0-48 months old infants and toddlers, Father's education level and smoking mother were both related to breast development. Breast development was significantly associated with physical growth, but had no correlation with the mental or psychomotor development.
authors.affiliation: Department of Developmental and Behavioral Pediatrics, Shanghai Children's Medical Center Affiliated to Shanghai Jiao Tong University School of Medicine, Ministry of Education Shanghai Key Laboratory of Children's Environmental Health, Shanghai 200127, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Aiping
authors.initials: A
authors.lastname: Wang
authors.forename: Lifang
authors.initials: L
authors.lastname: Kong
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.forename: Suyue
authors.initials: S
authors.lastname: Li
authors.forename: Yun
authors.initials: Y
authors.lastname: Liu
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.forename: Ruifang
authors.initials: R
authors.lastname: Zhang
authors.forename: Caixia
authors.initials: C
authors.lastname: Ban
authors.forename: Yanrui
authors.initials: Y
authors.lastname: Jiang
authors.forename: Wanqi
authors.initials: W
authors.lastname: Sun
authors.forename: Yuanjin
authors.initials: Y
authors.lastname: Song
authors.affiliation: Email: fanjiang@shsmu.edu.cn.
authors.forename: Fan
authors.initials: F
authors.lastname: Jiang
mesh_terms: D044383:Black People; D001827:Body Height; D001835:Body Weight; D001940:Breast / Q000254:growth & development*; D002657:Child Development; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004781:Environmental Exposure; D005260:Female; D006177:Gynecomastia / Q000453:epidemiology* / Q000209:etiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015999:Multivariate Analysis; D015995:Prevalence; D011629:Puberty, Precocious / Q000453:epidemiology* / Q000209:etiology