Which anthropometric measures best reflect neonatal adiposity?

BACKGROUND: Studying the determinants and the long-term consequences of fetal adipose accretion requires accurate assessment of neonatal body composition. In large epidemiological studies, in-depth body composition measurement methods are usually not feasible for cost and logistical reasons, and there is a need to identify anthropometric measures that adequately reflect neonatal adiposity. METHODS: In a multiethnic Asian mother-offspring cohort in Singapore, anthropometric measures (weight, length, abdominal circumference, skinfold thicknesses) were measured using standardized protocols in newborn infants, and anthropometric indices (weight/length, weight/length(2) (body mass index, BMI), weight/length(3) (ponderal index, PI)) derived. Neonatal total adiposity was measured using air displacement plethysmography (ADP) and abdominal adiposity using magnetic resonance imaging (MRI). Correlations of the anthropometric measures with ADP- and MRI-based adiposity were assessed using Pearson's correlation coefficients (r(p)), including in subsamples stratified by sex and ethnicity. RESULTS: Study neonates (n = 251) had a mean (s.d.) age of 10.2 (2.5) days. Correlations between ADP-based fat mass (ADPFM) and anthropometric measures were moderate (rp range: 0.44-0.67), with the strongest being with weight/length, weight, BMI and sum of skinfolds (r(p) = 0.67, 0.66, 0.62, 0.62, respectively, all P < 0.01). All anthropometric measures except skinfold thicknesses correlated more strongly with ADP- based fat-free mass than ADP(FM), indicating that skinfold measures may have more discriminative power in terms of neonatal total body adiposity. For MRI-based measures, weight and weight/length consistently showed strong positive correlations (r(p) >= 0.7) with abdominal adipose tissue compartments. These correlations were consistent in boys and girls, across different ethnic groups, and when conventional determinants of neonatal adiposity were adjusted for potential confounding. Abdominal circumference was not strongly associated with ADPFM or abdominal fat mass. CONCLUSIONS: Simple anthropometric measures (weight and weight/length) correlated strongly with neonatal adiposity, with some evidence for greater discriminative power for skinfold measures. These simple measures could be of value in large epidemiological studies.