Weight growth velocity of very low birth weight infants: role of gender, gestational age and major morbidities.

It's well known that VLBWI fail to thrive, however it's still unclear how gender, GA and morbidities affect growth pattern: aim of this study is to assess the influence of these factors on weight growth. 262 VLBWI were selected. Weight was recorded daily up to 28 days, weekly up to discharge and during 7 scheduled follow-up visits up to 2 years of corrected age. Individual profiles were fitted with a mathematical function suitable to model selected growth milestones and mean distance and velocity curves were drawn. Effects of gender, GA, major-morbidities, nutritional and respiratory support on individual weight growth milestones were estimated using a multivariate linear model. Each of these variables acts differently on weight growth pattern mainly modifying velocity curves characteristics. In particular, infants with major morbidities weight growth impairment-seen on distance curves at 2 years of corrected age-depends on poor weight velocity during a critical period ending within 4th month of postnatal age, for SGA or BPD infants, starting from 5th month of postnatal for severely neurologically impaired infants. These critical periods could be the most appropriate to identify risk factors for weight growth impairment in VLBWI.