Reliability of routine anthropometric measurements to estimate body composition in term infants.

ABSTRACT

BACKGROUND: Birth weight percentiles provide limited information on qualitative infant growth. Body composition provides estimates of fat mass, fat-free mass, and body fat percentage (adiposity). We sought to implement assessment of body composition at birth into clinical practice using a validated anthropometric equation and to evaluate measurement reliability. METHODS: Body composition was incorporated into newborn nursery admission procedure. Body fat percentage derived from skinfold measurements performed by clinical nurses were compared to a historical database of similar measurements performed on newborns by experienced research staff. Body Mass Index (BMI) and Ponderal Index (PI) were used as surrogates for adiposity. Comparison of correlations between groups assessed measurement reliability. P < 0.05 was considered significant. RESULTS: Nine hundred and ninety-one infants had body composition evaluated. Correlations were similar between BMI and %BF for measurements performed by research and clinical nurses (r2 = 0.82 versus r2 = 0.80; P = 0.142 for the difference between correlation coefficients) demonstrating good reliability. Similar results were found using PI (r2 = 0.58 versus r2 0.53; P = 0.105). CONCLUSIONS: Body composition can be assessed at birth using a validated anthropometric equation. Measurements performed by clinical RNs were found to be reliable, allowing for a qualitative measure of growth beyond birth weight. IMPACT Assessment of neonatal body composition at birth can be implemented into routine clinical practice using an anthropometric equation to estimate fat free-mass, fat mass, and percentage body fat. It provides a detailed, reproducible protocol to incorporate into routine practice. Assessment of fat mass, fat-free mass, and adiposity at birth allows for a qualitative measure of intrauterine growth beyond birth weight. Routine assessment of body composition provides a foundation for longitudinal follow-up of metabolic health in infancy and childhood.