Association of Low Birth Weight with Bone Mineral Density and Fracture Occurrence in Postmenopausal Women

Abstract Low birth weight (LBW) has been associated with impaired skeletal development and low peak bone mass. However, the association between LBW and fracture risk in postmenopausal women remains un-clear. We analyzed prospectively collected data from the population-based Osteoporosis Risk Factor and Pre-vention (OSTPRE) cohort, including women aged >50 years. Birth weight was categorized as LBW (<2500 g) or normal birth weight (≥2500 g). Fracture outcomes were analyzed using standardized inci-dence ratios (SIRs) with 95% confidence intervals (CIs). Bone mineral density (BMD) trajectories were assessed using linear mixed-effects models. There were 635 women in the LBW group and 9387 in the normal birth weight group. During follow-up, a total of 8453 fractures occurred. Women with LBW had an 18% higher risk of vertebral fractures (SIR 1.18, 95% CI 1.01–1.39), a 20% higher risk of vertebral or hip fractures combined (SIR 1.20, 95% CI 1.06–1.38), and an 11% higher risk of any osteoporotic fracture (SIR 1.11, 95% CI 1.01–1.22) compared with women with normal birth weight. Hip fracture risk was borderline increased (SIR 1.25, 95% CI 0.99–1.59). No significant differences in BMD levels or age-related BMD decline were observed between the groups. LBW was associated with increased fracture risk in postmenopausal women despite similar BMD trajecto-ries. These findings suggest that adverse early-life conditions may have long-term effects on skeletal fra-gility independent of later-life BMD.