First Year Metabolic and Hormonal Behavior Define two Different Populations of SGA Newborn for Weight or Height.

Context: Small-for-gestational-age (SGA) children have a particular metabolic and hormonal pattern at birth that changes rapidly. Objective: To evaluate the linear and weight growth in the first year of life in SGA children. Design: Prospective, monocentric cohort study. Setting: Real-world data collected from April 2012 to January 2016. Patients: SGA newborns uniformly defined by either growth or length lower than -2 SDs for gestational age. Interventions: All children were evaluated for 1 year after birth, at 3 days of life, then 3, 6, and 12 months after birth. Main outcome measures: Anthropometric parameters and biochemical variables, such as blood glucose, insulin, leptin, IGF-1, IGF binding protein-3 (IGFBP-3), and homeostasis model assessment - insulin resistance (HOMA-IR) index. Results: A total of 133 SGA children were enrolled. Length significantly improved 1 month after birth, whereas weight significantly increased only at 3 months after birth. Biochemical variables increased during the first year of life, showing a prediction by IGFBP-3 and HOMA-IR index. Then, the variables were divided considering either weight, length, or both, showing a different incidence. The biochemical variable changes recorded in the first step were maintained considering SGA children for weight or length, whereas they disappeared when weight and length were considered together. Conclusions: Our study shows a specific catchup growth for weight and length in SGA children. Moreover, we highlight that weight and length should be considered as independent parameters in SGA children, defining 2 different metabolic-hormonal populations with different conceivable predictive role in early catchup growth and in later growth and metabolic status.