title: Lactation is associated with greater maternal bone size and bone strength later in life.
abstract: CONCLUSIONS
  The association between lactation and bone size and strength was studied in 145 women 16 to 20 years after their last parturition. Longer cumulative duration of lactation was associated with larger bone size and strength later in life.
  
  
  BACKGROUND
  Pregnancy and lactation have no permanent negative effect on maternal bone mineral density but may positively affect bone structure in the long term. We hypothesized that long lactation promotes periosteal bone apposition and hence increasing maternal bone strength.
  
  
  METHODS
  Body composition, bone area, bone mineral content, and areal bone mineral density of whole body and left proximal femur were assessed using DXA, and cross-sectional area and volumetric bone mineral density of the left tibia shaft were measured by pQCT in 145 women (mean age 48 years, range 36-60 years) 16 to 20 years after their last parturition. Hip (HSI) and tibia strength indexes (TBSI) were calculated. Medical history and lifestyle factors including breastfeeding patterns and durations were collected via a self-administered questionnaire. Weight change during each pregnancy was collected from personal maternity tracking records.
  
  
  RESULTS
  Sixteen to 20 years after the last parturition, women who had breastfed in total more than 33 months in their life, regardless of the number of children, had greater bone strength estimates of the hip (HSI = 1.92 vs. 1.61) and the tibia (TBSI = 5,507 vs. 4,705) owing to their greater bone size than mothers who had breastfed less than 12 months (p < 0.05 for all). The differences in bone strength estimates were independent of body height and weight, menopause status, use of hormone replacement therapy, and present leisure time physical activity level.
  
  
  CONCLUSIONS
  Breastfeeding is beneficial to maternal bone strength in the long run.
authors.affiliation: Department of Health Sciences, University of Jyväskylä, P.O. Box 35 (LL), 40014, Jyväskylä, Finland.
authors.forename: P K
authors.initials: PK
authors.lastname: Wiklund
authors.forename: L
authors.initials: L
authors.lastname: Xu
authors.forename: Q
authors.initials: Q
authors.lastname: Wang
authors.forename: T
authors.initials: T
authors.lastname: Mikkola
authors.forename: A
authors.initials: A
authors.lastname: Lyytikäinen
authors.forename: E
authors.initials: E
authors.lastname: Völgyi
authors.forename: E
authors.initials: E
authors.lastname: Munukka
authors.forename: S M
authors.initials: SM
authors.lastname: Cheng
authors.forename: M
authors.initials: M
authors.lastname: Alen
authors.forename: S
authors.initials: S
authors.lastname: Keinänen-Kiukaanniemi
authors.forename: S
authors.initials: S
authors.lastname: Cheng
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000328:Adult; D000886:Anthropometry / Q000379:methods; D001823:Body Composition; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000033:anatomy & histology* / Q000502:physiology; D001942:Breast Feeding; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000502:physiology; D006801:Humans; D007774:Lactation / Q000502:physiology*; D008875:Middle Aged; D012189:Retrospective Studies; D013977:Tibia / Q000033:anatomy & histology / Q000502:physiology; D013997:Time Factors