title: Age at menarche: Influences of prenatal and postnatal growth.
abstract: OBJECTIVE
  The objective of this study was to determine the influence of birth weight and postnatal weight gain on age at menarche.
  
  
  METHODS
  This was a prospective cohort study where girls from the West Australian Pregnancy (Raine) Cohort Study were followed prospectively from fetal life (18 wk of pregnancy) to adolescence (12-14 yr).
  
  
  METHODS
  Age at menarche was the main outcome measure.
  
  
  RESULTS
  Growth status at birth was judged by expected birth weight ratio (EBW; a ratio of observed infant's birth weight over median birth weight appropriate for maternal age, weight, height, parity, infant sex, and gestational age). Postnatal growth status was judged by body mass index (BMI). Both EBW (P = 0.020) and BMI in childhood (8 yr of age) (P < 0.001) were associated with age at menarche. Menarche occurred earlier in girls with lower EBW and higher BMI.
  
  
  CONCLUSIONS
  We have demonstrated for the first time that both birth weight and weight gain in childhood are associated with age at menarche. Weight gain before birth and subsequent weight gain up to the age of 8 yr were found to have opposing influences on the timing of menarche. Lower EBW combined with higher BMI during childhood predicted early age at menarche, and this relationship existed across normal birth weight and BMI ranges.
authors.affiliation: School of Women's and Infants' Health, The University of Western Australia, Perth, Western Australia 6008, Australia d.sloboda@auckland.ac.nz
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Sloboda
authors.forename: Roger
authors.initials: R
authors.lastname: Hart
authors.forename: Dorota A
authors.initials: DA
authors.lastname: Doherty
authors.forename: Craig E
authors.initials: CE
authors.lastname: Pennell
authors.forename: Martha
authors.initials: M
authors.lastname: Hickey
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001724:Birth Weight; D015992:Body Mass Index; D002648:Child; D005260:Female; D006128:Growth; D006801:Humans; D007231:Infant, Newborn; D008572:Menarche; D011446:Prospective Studies; D015430:Weight Gain