Growth data prospectively collected on 1665 infants [birthweight (BW) 501-1500 g] by the 12 Network centers were used to evaluate velocity growth. Infants had been admitted to a Network NICU between 8/31/94 and 8/9/95 at age≤ 24 hrs, survived > 7 d, and were free of major congenital anomalies. They were followed until discharge, transfer, age 120 d or until reaching a body weight (WT) of 2000 g. WT was recorded daily until BW was regained and/or a minimum of 14 d, then it was recorded weekly; length (L), head circumference(HC), and midarm circumference (MAC) were recorded weekly. A random effects regression model which included time, log (time), and other covariates [eg gestational age (GA)] was used to analyze these longitudinal data and to construct velocity growth curves for infants within 100 g BW groups(Figure). Statistically significant correlations between the velocity of WT gain, L gain, HC gain, MAC gain, and MAC/HC ratio were noted. Within each 100 g BW group, GA, race and gender had no effect on the rate of growth. These curves were derived from a large, diverse population of VLBW infants. They will be useful to assess growth and to monitor the response to nutritional interventions.

figure 1

Figure 1