Effects of multiparity and duration of breast-feeding on maternal bone mineral density in post-menopausal Kurdish women: A retrospective study

Introduction: There is considerable amount of controversy about the long term effects of multiparity and duration of breastfeeding on maternal bone mineral density after menopause. This study was conducted to determine whether multiple pregnancy and prolonged duration of breast-feeding are independent predictors of low bone mass in post-menopausal Kurdish women. Methods: In a retrospective study, we evaluated 991 post-menopausal women with mean age of 58.9 years screened for osteoporosis by dual energy X-ray absorptiometry (DXA). According to the parity (1-2, 3-4, 5-7, >7 children) and total duration of breast-feeding (1-24, 25-60, 61-96, >96 months) they were classified. Bone mineral density (BMD) results for femoral neck and lumbar spine were classified into three groups (normal, osteopenia, and osteoporosis) according to the WHO criteria. Binary logistic regression was used to assess the independent associations of low femur or spine BMD with parity and total duration of breast-feeding. Results: We found that women with 5 or more children and having more than 60 months history of total breast-feeding, were older (p<0.001) with higher prevalence of osteoporosis (p<0.001). However, after adjusting for age only parity was independent predictor for osteopenia (OR: 1.336; 95% CI 1.29-1.735) while total duration of breast-feeding was not an independent predictor of low bone mass. Conclusion: Multiparity has a detrimental effect on maternal BMD. History of multiple pregnancy is a risk factor for low bone mass in post-menopausal women. However, prolonged duration of breast-feeding has no long-term adverse effect on maternal BMD in post-menopausal age.