title: [Age of pubertal events in Chilean school age girls and its relationship with socioeconomic status and body mass index].
abstract: BACKGROUND
  Recent studies in the United States have demonstrated that a significant proportion of girls show thelarche before the age of eight years. Nutritional status, geographic influences and racial factors are known to affect the timing of puberty.
  
  
  OBJECTIVE
  To evaluate the age of onset of puberty, development of secondary sexual characteristics and menarche in Chilean girls, and its relation to obesity and socioeconomic status.
  
  
  METHODS
  Healthy girls attending elementary school, from first to ninth grade in Santiago, Chile, were studied. A pediatric endocrinologist evaluated pubertal development using Tanner classification. Breast development was assessed by inspection and breast palpation. Average age of onset of pubertal events was determined by probit analysis.
  
  
  RESULTS
  A total of 758 girls, aged 5.8 to 16.1 years, were recruited. Obesity, defined as a BMI greater than 90th percentile, was found in 24.4%. The age of menarche was 12.7 years, the onset of Tanner stage 2 breast development and pubic hair was at 8.9 and 10.4 years, respectively. Sixteen percent of girls aged 7 to 7.9 years, had thelarche. Upper class girls showed a later onset of breast Tanner stage 4 stage than low-middle class girls. Obesity was not found in logistic regression analysis to be a significant predictive factor in the onset of puberty.
  
  
  CONCLUSIONS
  The age of menarche has not changed in the last thirty years, but an earlier onset of thelarche has occurred. The high frequency of thelarche between 7 and 8 years suggests that the normal age of breast development should be revised.
authors.affiliation: Instituto de Investigaciones Materno Infantil, Facultad de Medicina, Universidad de Chile y Hospital Clínico San Borja Arriarán, Servicio de Salud Metropolitano Centro, Santiago. ecodner@med.uchile.cl
authors.forename: Ethel
authors.initials: E
authors.lastname: Codner
authors.forename: Nancy
authors.initials: N
authors.lastname: Unanue
authors.forename: Ximena
authors.initials: X
authors.lastname: Gaete
authors.forename: Alvaro
authors.initials: A
authors.lastname: Barrera
authors.forename: Dennis
authors.initials: D
authors.lastname: Mook-Kanamori
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Bazaes
authors.forename: Alejandra
authors.initials: A
authors.lastname: Avila
authors.forename: Fernando
authors.initials: F
authors.lastname: Cassorla
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D015992:Body Mass Index; D001940:Breast / Q000254:growth & development; D002648:Child; D002677:Chile; D003430:Cross-Sectional Studies; D005260:Female; D006197:Hair / Q000254:growth & development; D006801:Humans; D008572:Menarche; D011627:Puberty / Q000502:physiology*; D012741:Sexual Maturation / Q000502:physiology*; D012923:Social Class; D012959:Socioeconomic Factors
vernacular_title: Cronología del desarrollo puberal en niñas escolares de Santiago: relación con nivel socio-económico e índice de masa corporal.