Body composition in human infants at birth and postnatally

The predictive values of anthropometric measurements, race, gender, gestati onal and postnatal ages, and season at birth and at study for the total bod y dual energy X-ray absorptiometry (DXA)-derived lean mass (LM), fat mass ( FM) and fat mass as a percentage of body weight (%FM) were determined in 21 4 singleton appropriate birth weight for gestational age infants [101 Cauca sian (60 boys, 41 girls) and 113 African American (55 boys, 58 girls)]. Ges tational ages were 27-42 wk and the infants were studied between birth and 391 d, weighing between 851 and 13446 g. In addition, predictive value of b ody weight, LM and FM for DXA bone measurements was also determined. Scan a cquisition used Hologic QDR 1000/W densitometer and infant platform and sca ns without significant movement artifacts were analyzed using software 5.64 p. Body weight, length, gender and postnatal age were significant predictor s of LM (adjusted R-2 >0.94) and FM (adjusted R-2 >0.85). Physiologic varia bles had little predictive value for %FM except in the newborns (adjusted R -2 0.69). Body weight was the dominant predictor of LM and FM, although len gth had similar predictive value for LM with increasing postnatal age. Fema le infants had less LM and more FM throughout infancy (P < 0.01). LM or FM offered no advantage over body weight in the prediction of bone mass measur ements. DXA is a useful means with which to determine body composition, and our data are important in the design and assessment of nutritional interve ntion studies.