A comparative study of postnatal anthropometric growth in very preterm infants and intrauterine growth

Abstract

Most growth references for very preterm infants were developed using measurements taken at birth, and were thought to represent intrauterine growth. However, it remains unclear whether the goal of approximating an intrauterine growth rate as stated by the American Academy of Pediatrics is attainable by very preterm infants. Using real-world measurement data from very preterm infants born between 2010 through 2020, we develop models to characterize the patterns of postnatal growth, and compare them to intrauterine growth. By assessing the weight growth rate, we show three phases of postnatal growth not evident in intrauterine growth. Furthermore, postnatal length and head circumference growth exhibit a slow rate after birth, followed by an acceleration. Collectively, postnatal and intrauterine growth are distinctly different. Although postnatal growth models do not represent optimal growth of very preterm infants, they can serve as a practical tool for clinical assessment of growth and for nutrition research.

Expected and Desirable Preterm and Small Infant Growth Patterns

“…The extent of weight loss depends on the infant’s fluid management [ [43] , [44] , [45] ]. This phase, characterized by an initial weight loss followed by growth, manifests on growth charts as decelerated growth when compared to the continuously ascending curves for all 3 metrics: weight, length, and head circumference, for the first few weeks of life ( Figures 2 , 3 ) [ 42 , 43 , [46] , [47] , [48] , [49] ]. During or following this initial physiological fluid adjustment, preterm infants commence growth, contingent on their nutritional intake and various other care-related factors.…”

An Open-Source Platform to Guide Implementation of the Postnatal Growth Charts for Preterm Infants

“…More recently, Chou et al utilized a large dataset from a cohort of 89,218 preterm infants born between 2010 and 2020, with a gestational age ranging from 22 4/7 to 30 3/7 weeks, to provide a comprehensive description of postnatal growth. [5] In Chou's study, they took a step further to compare postnatal and intrauterine growth. In Chou's study, infants were grouped by sex and gestational age (GA).…”

“…Standard deviations for each daily of life (DOL) were calculated accordingly (please refer to Ref. [5] for detailed calculation). Z-scores, the distance between measurement value and the mean estimate relative to the standard deviation, for any given measurement on DOL i can be calculated as follows: Furthermore, measurement estimates for any given Z-score can be derived as follows:…”