Background: Small for gestational age (SGA) neonates are prone to growth deficits in early life, which may be associated with later life metabolic abnormalities.
Objectives: To compare anthropometry and body composition using air-displacement plethysmography (ADP) in term SGA and appropriate for gestational age (AGA) neonates, and assess if sexual dimorphism existed in estimates of body composition.
Study design: Cross-sectional analytical study.
Participants: 413 term neonates (91 SGA and 322 AGA) at birth (≤7days).
Methods: Neonatal anthropometry and body composition were measured using ADP. Length corrected fat mass index (FMI) and fat free mass index (FFMI) were calculated.
Outcome: Anthropometry and body composition estimates of SGA and AGA neonates, segregated by sex.
Results: The mean (SD) birth weight of SGA and AGA neonates was 2.5 (0.2) kg and 3.1 (0.3) kg, respectively. SGA neonates had significantly lower % body fat (BF) (2.0%), fat mass (94.4 g), fat free mass (FFM) (349.7 g), FMI (0.34 kg/m2), and FFMI (0.76 kg/m2), but higher %FFM (2.0%) compared to AGA neonates (P<0.001). Males had significantly higher %FFM [91.2 (3.1) vs 90.2 (3.5); P=0.001], FFM [2604 (280) vs 2442 (233) g; P<0.001], and FFMI [11.1 (0.8) vs 10.8 (0.8) kg/m2; P=0.005], but lower % BF [8.8 (3.1) vs 9.8 (3.5); P=0.001] and FMI [1.1(0.4) vs 1.2 (0.5) kg/m2; P=0.008], compared to females.
Conclusions: Accurate estimates of body composition in neonates at birth suggest significantly lower body fat and fat free mass in SGA compared to AGA, with sexual dimorphism.