47 Postnatal Growth Kinetics of Very Low Birth Weight Infants

General agreement has been achieved on the need for longitudinal studies to evaluate growth of VLBWIs: these could provide data suitable to trace distance growth charts and also velocity charts so to detect earlier whether a child is growing unsatisfactorily. For this reason aim of this study has been to analyse weight growth kinetics of VLBWIs from birth up to 2 years. Data were prospectively collected on 262 VLBWIs admitted to Turin University NICU. During hospitalization body weight was recorded daily up to 28 days, then weekly up to discharge. Follow-up examinations were at 1–3-6–9-12–18-24 months of corrected age. The large number of weight measures per neonate allowed us to design an exponential-logistic function suitable for driving average weight growth and growth velocity curves. Weight growth curve of post-natal age has been plotted on the neonatal reference chart for N-W Italy and on the Italian longitudinal growth charts for children: weight is between the 10th and 25th centile at birth, at 42 weeks it is slightly below the 10th centile and it remains between the 10th and 25th centile up to 24 months. At 2 years population fails to achieve catch-up growth. The very complex pattern of weight growth is better described by the growth velocity curve: It shows a negative value of velocity in the first week, subsequently velocity increases and reaches a first narrow peak at 20.5 days and a second higher peak at 87.5 days. Then velocity decreases slowly and regularly. The function allowed us to describe some milestones of growth process. Growth velocity curve allowed us to demonstrate a non-linear growth kinetics for VLBWIs so it does not seem appropriate to report only a mean value of velocity as most authors do. Future studies should be performed to evaluate effects on growth kinetics exercised by individual pathologic variables.