Standardizing outcome measures in preterm infant nutrition research: Use of anthropometry and body composition in the neonatal intensive care unit.

Nutritional care and growth patterns in the neonatal intensive care unit (NICU) can impact lifelong health. Standardized measurement and reporting of growth outcomes are critical to improve the quality of information generated in research and population surveillance, facilitate comparisons and meta-analyses across individual studies, and strengthen the evidence used to generate clinical practice recommendations. Anthropometrics, specifically weight, length, and head circumference, are feasible and practical methods to monitor nutritional status. For research purposes, we recommend these anthropometrics be measured at birth (as a measure of fetal growth), 28 days old (to assess short-term growth), and 36 weeks postmenstrual age (PMA) (to determine the postnatal growth pattern in the NICU). We also encourage recording number of days to regain birthweight as a measure of short-term growth. Research publications should describe clearly the methods used to measure anthropometrics and reference curves used to calculate z-scores. Body composition is a complementary marker of nutritional status, but currently validated techniques have practical limitations in the NICU. When body composition tools are available, fat-free mass and fat mass should be measured at ∼36 weeks PMA. We also describe key knowledge gaps and research priorities regarding growth patterns of preterm infants in the NICU.