Parity and lactation are not associated with incident fragility fractures or radiographic vertebral fractures over 16years of follow-up: Canadian Multicentre Osteoporosis Study (CaMos).

Abstract

Pregnancy and especially lactation cause loss of bone mass and microarchitectural changes, which temporarily increase fracture risk. After weaning, aBMD increases but skeletal microarchitecture may be incompletely restored. Most retrospective clinical studies found neutral or even protective associations of parity and lactation with fragility fractures, but prospective data are sparse. CaMos is a randomly selected observational cohort that includes ~ 6500 women followed prospectively for over 16years. We determined whether parity or lactation were related to incident clinical fragility fractures over 16years, radiographic (morphometric and morphologic) vertebral fractures over 10years, and aBMD change (spine, total hip, and femoral neck) over 10years. Parity and lactation duration were analyzed as continuous variables in predicting these outcomes using univariate and multivariate regression analyses. Three thousand four hundred thirty-seven women completed 16years of follow-up for incident clinical fractures, 3839 completed 10years of morphometric vertebral fracture assessment, 3788 completed 10years of morphologic vertebral fracture assessment, and 4464 completed 10years of follow-up for change in aBMD. In the multivariate analyses, parity and lactation duration showed no associations with clinical fragility fractures, radiographic vertebral fractures, or change in aBMD, except that parity associated with a probable chance finding of a slightly greater decline in femoral neck aBMD. Parity and lactation have no adverse associations with clinical fragility or radiographic vertebral fractures, or the rate of BMD decline over 10years, in this prospective, multicenter study of a randomly selected, population-based cohort of women.