Supplementary Material for: Body Composition of Preterm Infants following Rapid Transition to Enteral Feeding

<b><i>Objective:</i></b> This study aimed to evaluate body composition at the time of hospital discharge in very preterm infants following rapid transition to full enteral feeding. <b><i>Study Design:</i></b> We conducted a prospective, observational, cross-sectional study and included 105 preterm infants &lt;32 gestational age or birth weight &lt;1,500 g, born between April 2015 and December 2020, following rapid transition to full enteral feeding (≥140 mL/kg/day). Fat mass/total body mass (BF%) and fat-free mass (FFM) were measured at the time of hospital discharge using air displacement plethysmography. <b><i>Results:</i></b> Median and interquartile range (Q1–Q3) of gestational age at birth (GA) was 27.3 (26.1–28.7) weeks and birth weight 845 (687–990) g. Time to reach full enteral feeding was 5 (5–7) days. At 37.6 weeks (36.1–39.0) postmenstrual age (PMA), BF% was 17.0% (14.9–19.8) and FFM 2,161 g (1,966–2,432). BF% was not associated with GA, and not different between small and appropriate for gestational age infants. FFM was significantly lower in infants born small for gestational age. <b><i>Conclusions:</i></b> Following rapid transition to full enteral feeding, FFM and BF% at discharge were similar to other preterm populations. BF% and FFM were not associated with GA at birth but with PMA at measurement. FFM was lower and BF% higher compared to term infants at birth, suggesting diminished parenchymal growth in preterm infants. Continued monitoring of body composition, metabolic health, and neurological development is needed to study long-term effects.