Is term newborn body composition being achieved postnatally in preterm infants?

Background: The American Academy of Pediatrics (AAP) recommends that preterm infants' growth duplicates fetal growth rates and that body composition replicates in utero body composition. Aims: To compare the total body fat mass between preterm infants assessed at term corrected age and full-term newborns, and to investigate the effects of gestational age, gender, weight increase, being breast fed on total adiposity. Study design: Prospective observational study. Subjects: One hundred and ten preterm infants [mean (SD) gestational age: 29.9 (2.3) weeks; birth weight: 1118 (274) g], and 87 full term [mean (SD) 38.6 (1.21) weeks, 3203 (385) g], breastfed infants. Outcome measures: Growth and body composition by means of a pediatric air displacement system were assessed at term corrected age in preterm infants and on day 3 of life in full term infants. Results: Weight, length and head circumference were smaller in the preterm group as compared to the term group. Mean (SD) percentage of fat mass in preterm infants was significantly higher as compared to term infants [14.8 (4.4) vs 8.59 (3.71), P <0.0001]. Fat mass was negatively correlated with gestational age (P <0.001), and positively associated with weight increase (P <0.05). Conclusions: Our data suggest that body composition, in terms of fat mass, in preterm infants at term corrected age is different from that of full term newborns.