Bone‐mass peak in multiparity and reduced risk of bone‐fractures in menopause

Abstract

OBJECTIVES: Pregnancy has been proposed as a risk factor for the development of osteoporosis; however, the results are controversial. Women in Colombia are multiparous, and therefore they represent an ideal population for the investigation of the effect of parity on osteoporosis. METHODS: The study included 1855 post-menopausal Hispanic women from Barranquilla, Colombia who were referred to our osteoporosis clinic for a routine evaluation of their bone mineral status. Bone mineral density (BMD, g/cm(2)) was measured using dual energy X-ray absorptiometry. Total body, femoral and lumbar areas were scanned. RESULTS: BMD of total body, hip and legs (P<0.0001), Ward's area (P<0.002) and intertrochanteric area (P<0.003) was high in women with at least one delivery in comparison with nulliparous women. Total mineral and calcium body contents were also high in women after second delivery. A history of fractures was found in 22.9% (n=425) of the study women. The relative risk for bone-fractures was high (O.R. 0.41; P<0.000002) in nulliparous women in comparison to multiparous women. In addition, osteopenia (O.R. 2.01; P=0.008) and osteoporosis (O.R. 3.99; P=0.0004) were most often present in nulliparous women in comparison to multiparous women. CONCLUSIONS: Pregnancies in this population appear to be a protective factor against development of osteoporosis. The increase in total mineral and calcium contents was related to the number of pregnancies, suggesting the existence of a bone mass peak during pregnancy.