Calculating postnatal growth velocity in very low birth weight (VLBW) premature infants

Abstract

ObjectiveCurrently, there is no standardized approach to the calculation of growth velocity (GV; g/kg/day) in hospitalized very low birth weight (VLBW) infants. Thus, differing methods are used to estimate GV, resulting in different medical centers and studies reporting growth results that are difficult to compare. The objective of this study was to compare actual GV calculated from infant daily weights during hospitalization in a Neonatal Intensive Care Unit (NICU) with estimated GV using two mathematical models that have previously been shown to provide good estimated GVs in extremely low birth weight infants: an exponential model (EM) and a 2-Point model (2-PM).Study DesignDaily weights from 81 infants with birth weights of 1000–1499g were used to calculate actual GV in daily increments from two starting points: (1) birth and (2) day of life of regaining birth weight. These daily GV values were then averaged over the NICU stay to yield overall NICU GV from the two starting points. We compared these actual GV with estimated GV calculated using the EM and 2-PM methods.ResultsThe mean absolute difference between actual and EM estimates of GV demonstrated <1% error for 100% of infants from both starting points. The mean absolute difference between actual and 2-PM estimates demonstrated <1% error for only 38% and 44% of infants from birth and regaining birth weight, respectively. The EM was unaffected by decreasing BW and increasing length of NICU stay, while the accuracy of the 2-PM was diminished significantly (p<.001) by both factors.ConclusionsIn contrast to the 2-PM, the EM provides an extremely accurate estimate of growth velocity in larger VLBW infants, and its accuracy is unaffected by common infant factors. The EM has now been validated for use in all VLBW infants to assess growth and provides a simple-to-use and consistent approach.

Weight Growth Velocity and Postnatal Growth Failure in Infants 501 to 1500 Grams: 2000–2013

“…The increase of 1.1 g/kg per day in average GV was We used the 2-point exponential model for calculating average GV described and validated by Patel et al 21,22 They compared calculating GV on the basis of the interval from birth to discharge as was done in the current study, with GV calculated by on the basis of the interval from the day on which birth weight was regained to discharge. Calculations based on the entire birth to discharge interval produced estimates of average GV that were ∼3 g/kg per day lower than values generated by using the day on which birth weight was regained as the starting point.…”

“…We used these weights to calculate an average GV over the NICU stay for each infant using the 2-point exponential model. 21,22 It is known that weight GV changes over the NICU stay. 27,28 Differences in the patterns of GV over the stay that would not be reflected in the average may be important.…”

“…21,22 The 2 points were birth weight and discharge weight. The Fenton growth charts were used to calculate the percentage of infants with postnatal growth failure, defined as a discharge weight less than the 10th percentile for postmenstrual age, and severe postnatal growth failure, defined as a discharge weight less than the third percentile for postmenstrual age.…”

Individualized fortification of breast milk in 41 Extremely Low Birth Weight (ELBW) preterm infants

“…where Wf is the weight at the end of fortification, W1 the weight at the beginning of fortification, Df − D1 the duration (days) of fortification and [(Wf + W1)2] the mean weight during fortification [23].…”

Effect of Nonnutritive Sucking and Oral Stimulation on Feeding Performance in Preterm Infants

“…Length of stay (d) was defined as the number of days from birth to discharge from the hospital. The average weight gain rate (%) in hospitalized preterm infants was calculated by the method proposed by Patel et al (24). We also recorded the illness degree using the NMI (Neonatal Medical Index) at admission to the NICU.…”