Introduction: Some evidence, but not all, has shown that higher birthweight is positively associated with bone density. Conversely, some evidence has shown that large for gestational age babies, or macrosomia, is associated with a reduced bone density (BMD) at birth. However, it is unknown if this pattern of association persists into childhood. Thus, we aimed to determine the association between macrosomia and bone mineral density in late childhood.
Methods: Women were recruited during pregnancy as part of the Vitamin D in Pregnancy Study at the University Hospital (formerly Geelong Hospital) antenatal clinic (n=475). At birth 400 mother-child pairs remained, 195 of whom returned at the 11-year follow-up and provided DXA measures (Lunar Prodigy). The regions of interest were Anterior-Posterior spine (L2-L4) and Total Body Less Head (TBLH). Macrosomia was defined as a birthweight equal to or greater than 4kg. Linear regression models were adjusted for maternal BMI during early pregnancy, child sex, and child pubertal stage. Models were then further adjusted for child’s current size parameters (height and weight).
Results: There were 185 mother-child pairs with complete information for the current analyses. 36 (19.5%) children were above 4kg. There was a positive association between macrosomia and child spine BMD (β:0.04; 95%CI:0.01,0.08), BMC (β:3.44; 95%CI:1.19,5.69), and TBLH BMD (β:0.04; 95%CI:0.01,0.06) and BMC (β:167.90; 95%CI:66.01,269.80). After adjustment for child’s current height and weight these associations were no longer significant.
Conclusion: In later childhood there was a positive association between macrosomia and bone mineral density. Thus, our data suggest that by age 11 years, there is an apparent positive association between macrosomia and BMD which is opposite direction to reports described at birth. This association appears to be largely driven by child’s current size parameters, likely owing to increased mechanical loading in larger children.