Determinants of body composition in preterm infants at the time of hospital discharge.

BACKGROUND Preterm infants have a higher fat mass (FM) percentage and a lower fat-free mass (FFM) than do term infants at the time of hospital discharge. OBJECTIVE We determined perinatal and nutritional factors that affect the body composition of preterm infants at discharge. DESIGN A total of 141 preterm infants born at <35 wk of gestation and admitted to Nantes University Hospital Neonatology Unit over a period of 2 y were enrolled. Nutritional intake and growth were monitored during hospitalization. Body composition was assessed by using air-displacement plethysmography at discharge. FFM was compared with reference data in term infants according to sex and gestational age. RESULTS Linear regression produced an excellent model to predict absolute FFM from perinatal characteristics and nutrition (R(2) = 0.82) but not the FM percentage (R(2) = 0.24). Gestational and postnatal ages played an equal role in absolute FFM accretion, as did the initial growth (between birth and day 5) and growth between day 5 and discharge. Antenatal corticosteroid treatment slightly reduced FFM accretion. As concerns nutritional intake, a higher protein:energy ratio at days 10 and 21 was significantly associated with decreased risk of an FFM deficit when preterm infants were compared with reference values for term infants. Boys had higher risk of an FFM deficit than did girls. CONCLUSION The initial growth and quality of nutrition were significantly associated with absolute FFM accretion during a hospital stay in preterm infants. This trial was registered at clinicaltrials.gov as NCT01450436.