Associations of Breastfeeding, Maternal Smoking, and Birth Weight With Bone Density and Microarchitecture in Young Adulthood: a 25-Year Birth-Cohort Study.

We have found that early-life exposures are associated with areal bone mineral density (aBMD) at ages 8 and 16 years. This study aimed to assess whether these associations persist into young adulthood when peak bone mass (PBM) is achieved and extend this analysis to microarchitecture. Participants were followed from perinatal period to 25 years old (n = 201). Outcomes were total body, spine, and hip aBMD (by dual-energy X-ray absorptiometry [DXA]), and cortical and trabecular bone measures at the distal radius and tibia (by high-resolution peripheral quantitative computed tomography [HRpQCT]). Early-life exposures including breastfeeding, maternal smoking during pregnancy, and birth weight. Sex, weight, height, vegetables, fruit and calcium intake at age 25 years were regarded as potential confounders in the analysis. There were significant interactions between period of gestation and early-life exposures for bone measures, so all analyses were stratified by period of gestation. Breastfeeding was beneficially associated with hip and total body aBMD, total, cortical and trabecular volumetric BMD (vBMD), cortical thickness, porosity, trabecular number (Tb.N), separation (Tb.Sp), and bone volume fraction (Tb.BV/TV) at radius and/or tibia at age 25 years in participants born prematurely (β ranged from -0.92 to 0.94), but there were no associations in those born at term. Maternal smoking had no association with any DXA/HRpQCT measures in those born prematurely but was detrimentally associated with inner transitional zone porosity and Tb.N (β = 0.40 and β = -0.37, respectively) in those full-term participants. Associations of birth weight with bone measures did not persist after adjustment for weight gain since birth. Breastfeeding was associated with a lower risk of lower limb fractures and maternal smoking had a deleterious association with upper limb fractures. In conclusion, breastfeeding and maternal smoking may have effects on peak bone microarchitecture whereas the association with birth weight is countered by subsequent growth. © 2020 American Society for Bone and Mineral Research.