Background and aims SGA preterm infants are likely to suffer from the high risk of body composition abnormalities in case of not optimal nutrition that may cause in the high risk for hypertonia, heart diseases and interconnected mortality, type 2 diabetes mellitus and obesity at adult age. The study aim was to estimate body composition and growth hormones of preterm infants of small- (SGA) and appropriate gestational age (AGA) at term equivalent age (38–42 weeks PCA).

Methods In the prospective study there was included: a) 140 newborn preterm AGA (birth weight from 10^th and 90^th percentile of the standardised growth scale) infants; b) 28 SGA (birth weight < 10^th percentile) infants. Growth hormones (insulin, insulin-like growth factor-1 (IGF-1), somatotrophic hormone, C-peptide, cortisol) and body composition of preterm infants were estimated by air plethysmography at term equivalent age.

Results SGA preterm infants had less length and body weight and Z-score in comparison with AGA preterm infants (p<0,01) in term equivalent age. Significant differences between head circumference in SGA and AGA infants at the term gestational age were not found. Estimated of body composition components showed equivalently high fat mass concentration (Fat mass, kg,%) in both groups of preterm infants. Higher concentration of insulin, IGF-1, C-peptide and cortisol in the blood sample was noted in SGA preterm infants (p<0,001). Moreover, SGA preterm infants had less concentration of somatotropin hormone having counterinsular and anabolic action in the blood sample comparing to AGA preterm infants (p<0,001).

Conclusion In the neonatal period, plastic processes happening against early beginning of ‘aggressive’ nutrition in both SGA and AGA preterm infants is characterised by the clear trend to strengthening adiponeogenesis.