Increments in Whole Body Bone Mineral Content Associated With Weight and Length in Pre-Term and Full-Term Infants During the First 6 Months of Life

Abstract

Background The objective of the present study was to assess bone mineral content (BMC) of the whole skeleton in pre-term and full-term healthy infants and the factors influencing BMC, such as bone area, birth weight, birth length, current weight, current length, gender, and gestational age. Methods Forty-eight healthy full-term infants and 34 healthy premature infants fed predominantly with intact human milk were studied. BMC was measured monthly with dual energy X-ray absorptiometry (DEXA). At the same time, length and weight were measured and registered. Pre-term infants were studied at 60-day intervals. Results For both full-term and pre-term infants, BMC increased during the first months of life. However, the values of pre-term infants never reached the values of full-term infants, even after correcting for age and weight. For both full-term and pre-term infants, BMC was significantly correlated at the second month with birth weight ( r = 0.901), birth length ( r = 0.860), gestational age ( r = 0.803), bone area ( r = 0.960), current weight ( r = 0.920), and current length ( r = 0.840, p <0.001 for all correlation coefficients). Multivariate analysis revealed that bone area was the most important factor in predicting BMC. Conclusions Pre-term children have lower BMC than full-term children. The main factor explaining this apparent osteopenia is bone area. Pre-term children have a higher daily mineralization rate than full-term children, but this catch-up mineralization is not enough to reach BMC levels seen in full-term children.