Lactation is associated with greater maternal bone size and bone strength later in life

Department of Health Sciences, University of Jyväskylä, P.O. Box 35 (LL), 40014, Jyväskylä, Finland.
Osteoporosis International (Impact Factor: 4.17). 09/2011; 23(7):1939-45. DOI: 10.1007/s00198-011-1790-z
Source: PubMed


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.
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.
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.
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.
Breastfeeding is beneficial to maternal bone strength in the long run.

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    • "After clustering cumulative lactation, we found differences in the aBMD at the trochanter. Our results are thus confirmatory of much larger epidemiological studies which have examined whether a history of lactation affects BMD or fracture risk later in life, and we obtained similar results [21–23]. "
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    ABSTRACT: During lactation abundant calcium is lost from the mother as a result of the amount of breast milk produced. Lactation leads to transient fragility, with some women experiencing even fragility fractures, but nearly all of these women subsequently undergo a large increase in bone mineral density (BMD), confirming that the BMD must have declined during lactation but it increases after weaning. We have retrospectively examined the relationship between the duration of breastfeeding and bone properties in Spanish premenopausal healthy women, to identify the site-specific changes in BMD. Four hundred and thirty-three premenopausal healthy women, 295 with a mean of 7.82 ±6.68 months of exclusive breastfeeding and 138 control women, were studied. We examined total, trabecular and cortical volumetric BMD (mg/mm(3)) at the distal radius using peripheral quantitative computed tomography. Areal BMD (g/cm(2)) was measured using dual energy X-ray absorptiometry at the femoral neck, lumbar spine, trochanter and Ward's triangle. Phalangeal bone ultrasound was measured by amplitude-dependent speed of sound. Areal BMD analysis at L2-L4 revealed significant intergroup differences (p < 0.05). There were significant intergroup differences in the volumetric BMD in both total and cortical bone (p < 0.05). The observed BMD of breast-feeders was higher than the BMD in non-breast-feeding women. Additionally, the lactation subgroup analysis revealed significant differences in the areal BMD at trochanter and L2-L4 (p < 0.05) and in the cortical volumetric BMD (p < 0.05). This study adds to the growing evidence that breastfeeding has no deleterious effects and may confer an additional advantage for BMD in premenopausal women.
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