Do anthropometric measures accurately reflect body composition in preterm infants?

Area of Science:

• Neonatal physiology
• Pediatric nutrition
• Body composition analysis

Background:

• Neonatal adiposity and lean mass predict later metabolic and cognitive health, respectively, in preterm infants.
• Accurate anthropometric indices for neonatal body composition are needed for clinical care and research.
• Existing indices have not been systematically validated in preterm infants.

Purpose of the Study:

• To identify the most effective weight/length indices for assessing neonatal body composition in preterm infants.
• To evaluate the validity of anthropometric proxies for fat-free mass (FFM), fat mass (FM), and percent body fat (%BF) at birth.

Main Methods:

• 218 preterm infants had body composition (FFM, FM, %BF) measured via air-displacement plethysmography within 72 hours of birth.
• Weight and length were recorded.
• Linear regression models assessed weight/length indices, using variance explained (R² ) and root mean square error (RMSE) to determine the best proxies.

Main Results:

• Body weight alone was a strong predictor of FFM (R² =0.97).
• Weight/length² was the best proxy for %BF, but explained little variance (R² =0.27) and had high prediction error (RMSE=3.5% fat).
• No tested weight/length index accurately reflected %BF.

Conclusions:

• Weight/length indices are unsuitable for assessing relative adiposity in preterm infants at birth.
• Body weight is an adequate surrogate for lean mass in preterm neonates.
• Further research is needed to establish reliable methods for assessing adiposity in preterm infants.