Journal of Osteoporosis and Physical Activity
Open Access

Abstract

The Effect of Parity on Bone Mineral Density in Postmenopausal Women: A Systematic Review

Alemayehu Bayray and Fikre Enquselassie

Introduction: Several reports have shown a positive correlation between parity and Bone Mineral Density (BMD) and a reduced hip fracture rate, although other studies have reported either no correlation between parity and Bone Mineral Density (BMD) or a negative correlation in postmenopausal women. Hence, a systematic review is needed to help clarify these discrepancies and determine the effect of parity on bone mineral density.

Objective: This study was designed to examine the effect of parity on bone mineral density in postmenopausal women.

Methodology: A systematic review of 19 published studies reporting the effect of parity on bone mineral density of 27,434 nulliparous and parous post menopausal women was conducted and a narrative analysis was made. A total of 356 articles were initially browsed (205 from Pub MED/Medline, 61 from HINARI, and 90 from Google scholar). All English titles and abstracts were scanned to eliminate duplicates and to assess for relevance. Additional references were found through bibliographic searches of all retrieved articles. Studies were included if they (a) examined effect of parity on BMD (by absorptiometry or quantitative ultrasound), (b) included post menopausal women.

Result: Out of nineteen studies eight of them, 1 cohort, 1 case control, and four comparative cross sectional studies, with a combined total of 17,077 subjects concluded that parity positively influences bone mineral density. In contrast to the papers who reported positive effects, six studies; 1 retrospective record review, 1 case control, and 6 comparative cross sectional with a combined total of 7,410 subjects concluded that there is a negative effect of parity on bone mineral density in the post menopausal women. Five comparative cross sectional studies with a combined total of 2,947 women reported that there is no effect of parity on bone mineral density in post menopausal women.

Conclusion and recommendations: The majority of the studies supports a positive effect of parity on BMD in postmenopausal women (with a combined total of 17,077 subjects), while, six studies support a negative effect of parity on BMD (with a combined total of 7,410 subjects). Furthermore five studies (of 2,947 women) did not find any effect. Because most of the studies found were of generally lower level evidence it was difficult to make firm conclusions. Hence, further robust, well designed observational studies should be carried out to confirm these results. Ideally, any future studies would also take into account for the consistent measurement and standardization of DEXA/QUS sites and categorization of parities.