title: Influence of number of deliveries and total breast-feeding time on bone mineral density in premenopausal and young postmenopausal women.
abstract: OBJECTIVE
  Pregnancy and lactation have been associated with decline in bone mineral density (BMD). It is not clear if there is a full recovery of BMD to baseline. This study sought to determine if pregnancy or breast-feeding or both have a cumulative effect on BMD in premenopausal and early postmenopausal women.
  
  
  METHODS
  We performed single-center cohort analysis. Five hundred women aged 35-55 years underwent routine BMD screening from February to July 2011 at a tertiary medical center. Patients were questioned about number of total full-term deliveries and duration of breast-feeding and completed a background questionnaire on menarche and menopause, smoking, dairy product consumption, and weekly physical exercise. Weight and height were measured. Dual-energy X-ray absorptiometry was used to measure spinal, dual femoral neck, and total hip BMD.
  
  
  METHODS
  Associations between background characteristics and BMD values were analyzed.
  
  
  RESULTS
  Sixty percent of the women were premenopausal. Mean number of deliveries was 2.5 and mean duration of breast-feeding was 9.12 months. On univariate analysis, BMD values were negatively correlated with patient age (p=0.006) and number of births (p=0.013), and positively correlated with body mass index (p<0.001). On multiple (adjusted) logistic regression analysis, prolonged breast-feeding duration, but not number of deliveries, was significantly correlated to a low BMD (p=0.008). An effect was noted only in postmenopausal women. The spine was the most common site of BMD decrease.
  
  
  CONCLUSIONS
  Prolonged breast-feeding may have a deleterious long-term effect on BMD and may contribute to increased risk of osteoporosis later in life.
authors: Institute of Endocrinology, Rabin Medical Center, Beilinson Hospital, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. Electronic address: Gloria.tsvetov@gmail.com.
authors: Gloria
authors: G
authors: Tsvetov
authors: Statistical Education Unit, The Academic College of Tel Aviv Yaffo, Israel.
authors: Sigal
authors: S
authors: Levy
authors: Institute of Endocrinology, Rabin Medical Center, Beilinson Hospital, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors: Carlos
authors: C
authors: Benbassat
authors: Institute of Endocrinology, Rabin Medical Center, Beilinson Hospital, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors: Ilana
authors: I
authors: Shraga-Slutzky
authors: Institute of Endocrinology, Rabin Medical Center, Beilinson Hospital, Petach Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors: Dania
authors: D
authors: Hirsch
mesh_terms: D000328:Adult; D000367:Age Factors; D015992:Body Mass Index; D015519:Bone Density; D001942:Breast Feeding; D015331:Cohort Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000209:etiology* / Q000378:metabolism; D010298:Parity; D017698:Postmenopause; D011247:Pregnancy; D017697:Premenopause; D013131:Spine / Q000378:metabolism*; D011795:Surveys and Questionnaires
keywords: Bone density; Breast-feeding; Osteoporosis; Pregnancy; Risk factors