Neonatal growth velocity of preterm infants: The weight Z-score change versus Patel exponential model

Abstract

Background Different methods are used to assess the growth of preterm infants during neonatal hospital stay. The primary objective was to compare two methods for assessing growth velocity: g/kg/d according to the Patel exponential model (EM) and change in weight z-score (ZS) according to Fenton curves. The secondary objective was to highlight factors influencing the level of agreement between the two methods. Methods Preterm infants born before 33 weeks were included. Growth velocity was computed by EM and ZS methods and linear regression was used to predict what growth velocity by EM method would be obtained using the ZS method. Differences between EM growth velocity and EM growth velocity predicted by ZS method were then used to assess the level of agreement between the two methods. A difference between -2 and +2 g/kg/day was considered as fair agreement, greater than ± 4 g/kg/day as poor agreement, and as disagreement otherwise. Results Among the 3954 children included, we observe a fair agreement in 2471 children (62.5%), a poor agreement in 1278 (32.3%) and a disagreement in 205 children (5.2%). Birth weight and gestational age explained 31% and 25%, respectively, of the variance in the difference between the two methods. Conclusions In more than a third of enrolled children, the two methods for measuring growth velocity disagreed substantially. As variation of weight Z-score takes into account infant gestational age and gender, it could be more suitable to analyze a population of preterm infants with a wide range of gestational age.

Postnatal growth of preterm infants during the first two years of life: catch-up growth accompanied by risk of overweight

“…Generalized estimating equation (GEE) models were used to analyze trajectory trends of these growth measurements over time. Growth velocity was defined as the change of z-score over the periods [ 15 , 16 ] using the lincom function of GEE models. Gestational age, gender, birth weight z-score, and intrauterine growth status was adjusted as covariates.…”

Association between postnatal growth and neurodevelopmental impairment by sex at 2 years of corrected age in a multi-national cohort of very preterm children

“…We used two EUGR indicators based on changes in weight between birth and discharge from the neonatal hospitalisation which are most commonly used in the scientific literature. [15][16][17][18] The first indicator was birthweight and discharge-weight Zscore differences using Fenton's postnatal growth charts (Fenton delta Z-score). 10 The second indicator uses an exponential model of growth velocity to measure the average gain in grams per kilogram (kg) of weight per day based on birthweight, discharge weight and number of days of hospitalization (Patel's weight-gain velocity).…”

“…Our analysis of the overlap between the groups found that risks were highest when boys were classified as severely EUGR by both measures and also moderately elevated when they were severely EUGR by Fenton. Fenton's delta Z-score has been considered by some researchers to be preferable because it adjusts for GA and sex, 17,46 whereas Patel's weight-gain velocity is calculated in the same manner for all neonates. 8 We do not know of any studies that have investigated the effect of combining information from both indicators.…”

Postnatal growth of preterm infants during the first two years of life: catch-up growth accompanied by risk of overweight

“…Generalized estimating equation (GEE) models were used to analyze trajectory trends of these growth measurements over time. Growth velocity was de ned as the change of z-score over the periods (15,16) using the lincom function of GEE models. Gestational age, gender, birth weight zscore, and intrauterine growth status was adjusted as covariates.…”