A hospital-based cohort study of gender and gestational age-specific body fat percentage at birth.

Background: Birthweight is the most commonly used proxy marker but does not adequately define true nutritional status. Modalities like DXA (dual energy x-ray absorptiometry) and TOtal Body Electric Conductivity (TOBEC) have been validated to assess body composition but their accuracy in neonates has not been established. The PEAPOD (COSMED, Rome Italy) has been validated as an accurate tool for measuring percentage body fat (%BF) in newborns. The study aim was to determine the gender-specific %BF percentiles at different gestations (35-41 weeks) for a healthy population of newborn infants. A secondary aim was to determine whether there is any relationship between %BF and neonatal condition at birth (cord gas measurement).
Methods: %BF was measured using air displacement plethysmography (PEAPOD) within 6 h of birth.
Results: There is an increase in the mean %BF with increasing gestation for female and males from 36 weeks' gestation in the 7667 infants who underwent assessment. Females have a higher %BF than their male equivalents. There was no correlation between %BF and cord pH.
Conclusion: Gender and gestation are both important in determining the quantiles and mean %BF at birth. There was no correlation between low cord pH and %BF.
Impact: Measuring the percentage body fat (PEAPOD) at birth is a useful marker of an infant's nutritional status. This is the largest hospital-based cohort of gestational age and gender-specific %BF in healthy newborns. The normative graphs from this study will help to accurately determine high-risk infants with low %BF so they can be monitored appropriately.