Body composition at birth in preterm infants between 30 and 36 weeks gestation

BackgroundThe American Academy of Pediatrics calls for aggressive management of preterm infants to achieve body composition approximating that of the healthy infant in utero. Air displacement plethysmography (ADP) has been validated for assessment of body composition in preterm infants and could be used to monitor their nutritional status during hospitalization. Comparative datasets on body composition at birth among healthy, live-born preterm infants are lacking. ObjectiveThe aim of this study is to provide the first descriptive fat mass (FM) and fat-free mass (FFM) data from healthy newborn preterm infants at birth as a proxy for healthy in utero body composition. MethodsBody mass and volume were obtained using ADP within 72h of birth in 98 singleton, appropriate-for-gestational-age preterm infants. FM and FFM were calculated using the Fomon equation. ResultsMeasurement with ADP was feasible and well tolerated by infants as young as 30 weeks gestation and <72h of age. FFM and FM increased linearly over the gestational age range period at rates of 171 and 46g week(-1), respectively. Mean values obtained by ADP by gestational week were similar to the previously published reference data from chemical analysis on stillbirths. ConclusionsBody composition assessment using ADP is feasible in newborn preterm infants and provides group estimates similar to that of the reference fetus. In the future, integrating body composition information into the nutritional management of preterm infants may help to identify new strategies to optimize growth and development in this vulnerable population.