NORMATIVE STANDARDS AND PATTERNING OF FAT AND MUSCLE IN WHITE AND BLACK NEWBORN INFANTS.

Abstract

Due to the lack of normative data in newborns, we report fat and muscle patterning, and standards for the sums of fat and muscle areas and muscle circumferences for arm, forearm, thigh, and calf in white and black newborn infants that may have clinical application in the assessment of body composition in newborns. Significant differences were found between white males and white females in fatness patterning: white female newborns were larger for all 21 variables except height. Statistically significant differences (t test; p < 0.05) existed for five skinfold measurements (forearm, subscapular, suprailiac, thigh, medial calf), three limb fat areas (forearm, thigh, calf), and the sums of the skinfolds and fat areas despite similar limb circumferences. Black female newborns were larger than black males for five of the eight skinfolds (with a significant difference observed in medial calf skinfold), for all of the limb fat areas, and for the sums of the skinfolds and fat areas. Despite their larger skinfolds and fat areas, black females had smaller circumferences. No sex-related trends or significantly different variables were observed in the muscle patterning of white infants. Differences in muscle patterning were observed between black males and black females, with males having larger values for all 14 variables. Statistically significant differences were found between white and black infants, with white newborns having greater height, medial calf skinfold, and calf fat area.